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	$210.33	5.771%	$222.4681	$222.47	$222.45	$222.50
Purchase #2	$29.84	10.813%	$33.0666	$33.07	$33.05	$33.10
Purchase #3	$26.90	5.758%	$28.4489	$28.45	$28.45	$28.40
Purchase #4	$173.34	5.215%	$182.3797	$182.38	$182.40	$182.40
Purchase #5	$214.70	11.276%	$238.9096	$238.91	$238.90	$238.90
Purchase #6	$68.38	4.808%	$71.6677	$71.67	$71.65	$71.70
Purchase #7	$233.48	3.735%	$242.2005	$242.20	$242.20	$242.20
7 purchase totals =	$956.97		$1,019.1411	$1,019.15	$1,019.10	$1,019.20