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	$37.30	11.543%	$41.6055	$41.61	$41.60	$41.60
Purchase #2	$232.27	7.326%	$249.2861	$249.29	$249.30	$249.30
Purchase #3	$184.43	6.765%	$196.9067	$196.91	$196.90	$196.90
Purchase #4	$222.28	9.373%	$243.1143	$243.11	$243.10	$243.10
Purchase #5	$152.25	5.406%	$160.4806	$160.48	$160.50	$160.50
Purchase #6	$86.87	7.757%	$93.6085	$93.61	$93.60	$93.60
Purchase #7	$131.63	7.649%	$141.6984	$141.70	$141.70	$141.70
7 purchase totals =	$1,047.03		$1,126.7001	$1,126.71	$1,126.70	$1,126.70