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	$191.49	10.129%	$210.886	$210.89	$210.90	$210.90
Purchase #2	$209.48	6.178%	$222.4217	$222.42	$222.40	$222.40
Purchase #3	$159.34	10.607%	$176.2412	$176.24	$176.25	$176.20
Purchase #4	$173.65	13.268%	$196.6899	$196.69	$196.70	$196.70
Purchase #5	$145.39	12.819%	$164.0275	$164.03	$164.05	$164.00
Purchase #6	$113.69	10.388%	$125.5001	$125.50	$125.50	$125.50
Purchase #7	$199.64	8.372%	$216.3539	$216.35	$216.35	$216.40
7 purchase totals =	$1,192.68		$1,312.1203	$1,312.12	$1,312.15	$1,312.10