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	$245.77	11.533%	$274.1147	$274.11	$274.10	$274.10
Purchase #2	$57.76	12.809%	$65.1585	$65.16	$65.15	$65.20
Purchase #3	$230.86	5.638%	$243.8759	$243.88	$243.90	$243.90
Purchase #4	$28.39	13.248%	$32.1511	$32.15	$32.15	$32.20
Purchase #5	$56.27	6.303%	$59.8167	$59.82	$59.80	$59.80
Purchase #6	$194.98	13.628%	$221.5519	$221.55	$221.55	$221.60
Purchase #7	$133.36	9.722%	$146.3253	$146.33	$146.35	$146.30
7 purchase totals =	$947.39		$1,042.9941	$1,043.00	$1,043.00	$1,043.10