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	$54.37	6.459%	$57.8818	$57.88	$57.90	$57.90
Purchase #2	$26.72	8.215%	$28.915	$28.92	$28.90	$28.90
Purchase #3	$217.58	11.654%	$242.9368	$242.94	$242.95	$242.90
Purchase #4	$238.44	11.360%	$265.5268	$265.53	$265.55	$265.50
Purchase #5	$50.62	7.392%	$54.3618	$54.36	$54.35	$54.40
Purchase #6	$247.74	6.657%	$264.2321	$264.23	$264.25	$264.20
Purchase #7	$161.72	11.235%	$179.8892	$179.89	$179.90	$179.90
7 purchase totals =	$997.19		$1,093.7435	$1,093.75	$1,093.80	$1,093.70