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	$214.37	11.241%	$238.4673	$238.47	$238.45	$238.50
Purchase #2	$93.30	5.147%	$98.1022	$98.10	$98.10	$98.10
Purchase #3	$168.32	9.770%	$184.7649	$184.76	$184.75	$184.80
Purchase #4	$72.72	11.770%	$81.2791	$81.28	$81.30	$81.30
Purchase #5	$102.96	7.767%	$110.9569	$110.96	$110.95	$111.00
Purchase #6	$132.79	3.268%	$137.1296	$137.13	$137.15	$137.10
Purchase #7	$210.37	5.774%	$222.5168	$222.52	$222.50	$222.50
7 purchase totals =	$994.83		$1,073.2168	$1,073.22	$1,073.20	$1,073.30