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	$85.92	3.300%	$88.7554	$88.76	$88.75	$88.80
Purchase #2	$92.52	13.612%	$105.1138	$105.11	$105.10	$105.10
Purchase #3	$46.73	11.149%	$51.9399	$51.94	$51.95	$51.90
Purchase #4	$32.58	9.603%	$35.7087	$35.71	$35.70	$35.70
Purchase #5	$131.31	12.834%	$148.1623	$148.16	$148.15	$148.20
Purchase #6	$248.97	6.380%	$264.8543	$264.85	$264.85	$264.90
Purchase #7	$147.94	8.192%	$160.0592	$160.06	$160.05	$160.10
7 purchase totals =	$785.97		$854.5936	$854.59	$854.55	$854.70