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	$148.71	5.124%	$156.3299	$156.33	$156.35	$156.30
Purchase #2	$189.70	7.405%	$203.7473	$203.75	$203.75	$203.70
Purchase #3	$11.77	4.672%	$12.3199	$12.32	$12.30	$12.30
Purchase #4	$236.89	11.181%	$263.3767	$263.38	$263.40	$263.40
Purchase #5	$95.68	4.410%	$99.8995	$99.90	$99.90	$99.90
Purchase #6	$193.29	11.204%	$214.9462	$214.95	$214.95	$214.90
Purchase #7	$171.61	11.226%	$190.8749	$190.87	$190.85	$190.90
7 purchase totals =	$1,047.65		$1,141.4944	$1,141.50	$1,141.50	$1,141.40