Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$218.57	13.282%	$247.6005	$247.60	$247.60	$247.60
Purchase #2	$155.97	7.871%	$168.2464	$168.25	$168.25	$168.20
Purchase #3	$160.70	11.759%	$179.5967	$179.60	$179.60	$179.60
Purchase #4	$201.51	10.604%	$222.8781	$222.88	$222.90	$222.90
Purchase #5	$148.34	5.340%	$156.2614	$156.26	$156.25	$156.30
Purchase #6	$94.73	7.541%	$101.8736	$101.87	$101.85	$101.90
Purchase #7	$91.64	12.722%	$103.2984	$103.30	$103.30	$103.30
7 purchase totals =	$1,071.46		$1,179.7551	$1,179.76	$1,179.75	$1,179.80