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	$35.72	12.551%	$40.2032	$40.20	$40.20	$40.20
Purchase #2	$187.40	4.568%	$195.9604	$195.96	$195.95	$196.00
Purchase #3	$89.25	11.496%	$99.5102	$99.51	$99.50	$99.50
Purchase #4	$48.48	3.795%	$50.3198	$50.32	$50.30	$50.30
Purchase #5	$211.57	8.365%	$229.2678	$229.27	$229.25	$229.30
Purchase #6	$175.90	10.262%	$193.9509	$193.95	$193.95	$194.00
Purchase #7	$221.79	5.113%	$233.1301	$233.13	$233.15	$233.10
7 purchase totals =	$970.11		$1,042.3424	$1,042.34	$1,042.30	$1,042.40