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	$151.83	13.152%	$171.7987	$171.80	$171.80	$171.80
Purchase #2	$234.28	13.480%	$265.8609	$265.86	$265.85	$265.90
Purchase #3	$140.92	6.814%	$150.5223	$150.52	$150.50	$150.50
Purchase #4	$156.85	9.851%	$172.3013	$172.30	$172.30	$172.30
Purchase #5	$58.94	9.866%	$64.755	$64.76	$64.75	$64.80
Purchase #6	$25.37	5.417%	$26.7443	$26.74	$26.75	$26.70
Purchase #7	$169.63	11.254%	$188.7202	$188.72	$188.70	$188.70
7 purchase totals =	$937.82		$1,040.7027	$1,040.70	$1,040.65	$1,040.70