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	$227.85	8.629%	$247.5112	$247.51	$247.50	$247.50
Purchase #2	$147.65	11.772%	$165.0314	$165.03	$165.05	$165.00
Purchase #3	$205.82	8.667%	$223.6584	$223.66	$223.65	$223.70
Purchase #4	$240.30	3.402%	$248.475	$248.48	$248.50	$248.50
Purchase #5	$178.31	9.816%	$195.8129	$195.81	$195.80	$195.80
Purchase #6	$98.61	12.722%	$111.1552	$111.16	$111.15	$111.20
Purchase #7	$77.30	6.790%	$82.5487	$82.55	$82.55	$82.50
7 purchase totals =	$1,175.84		$1,274.1928	$1,274.20	$1,274.20	$1,274.20