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	$201.58	13.740%	$229.2771	$229.28	$229.30	$229.30
Purchase #2	$242.89	12.442%	$273.1104	$273.11	$273.10	$273.10
Purchase #3	$182.98	7.154%	$196.0704	$196.07	$196.05	$196.10
Purchase #4	$239.58	10.619%	$265.021	$265.02	$265.00	$265.00
Purchase #5	$16.60	10.812%	$18.3948	$18.39	$18.40	$18.40
Purchase #6	$120.90	6.360%	$128.5892	$128.59	$128.60	$128.60
Purchase #7	$108.30	6.590%	$115.437	$115.44	$115.45	$115.40
7 purchase totals =	$1,112.83		$1,225.8999	$1,225.90	$1,225.90	$1,225.90