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	$73.67	8.425%	$79.8767	$79.88	$79.90	$79.90
Purchase #2	$158.76	4.234%	$165.4819	$165.48	$165.50	$165.50
Purchase #3	$228.61	11.635%	$255.2088	$255.21	$255.20	$255.20
Purchase #4	$78.84	4.344%	$82.2648	$82.26	$82.25	$82.30
Purchase #5	$88.84	11.795%	$99.3187	$99.32	$99.30	$99.30
Purchase #6	$47.42	13.305%	$53.7292	$53.73	$53.75	$53.70
Purchase #7	$191.54	5.596%	$202.2586	$202.26	$202.25	$202.30
7 purchase totals =	$867.68		$938.1387	$938.14	$938.15	$938.20