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	$36.61	13.140%	$41.4206	$41.42	$41.40	$41.40
Purchase #2	$53.94	9.867%	$59.2623	$59.26	$59.25	$59.30
Purchase #3	$189.36	3.197%	$195.4138	$195.41	$195.40	$195.40
Purchase #4	$55.79	3.170%	$57.5585	$57.56	$57.55	$57.60
Purchase #5	$212.42	4.572%	$222.1318	$222.13	$222.15	$222.10
Purchase #6	$218.85	13.613%	$248.6421	$248.64	$248.65	$248.60
Purchase #7	$53.86	13.850%	$61.3196	$61.32	$61.30	$61.30
7 purchase totals =	$820.83		$885.7487	$885.74	$885.70	$885.70