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	$209.96	11.224%	$233.5259	$233.53	$233.55	$233.50
Purchase #2	$161.29	3.406%	$166.7835	$166.78	$166.80	$166.80
Purchase #3	$88.76	11.834%	$99.2639	$99.26	$99.25	$99.30
Purchase #4	$151.52	6.179%	$160.8824	$160.88	$160.90	$160.90
Purchase #5	$10.62	13.585%	$12.0627	$12.06	$12.05	$12.10
Purchase #6	$183.80	9.296%	$200.886	$200.89	$200.90	$200.90
Purchase #7	$18.90	13.843%	$21.5163	$21.52	$21.50	$21.50
7 purchase totals =	$824.85		$894.9207	$894.92	$894.95	$895.00