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	$90.87	13.752%	$103.3664	$103.37	$103.35	$103.40
Purchase #2	$63.69	12.183%	$71.4494	$71.45	$71.45	$71.40
Purchase #3	$142.80	6.784%	$152.4876	$152.49	$152.50	$152.50
Purchase #4	$83.91	10.485%	$92.708	$92.71	$92.70	$92.70
Purchase #5	$223.29	10.275%	$246.233	$246.23	$246.25	$246.20
Purchase #6	$240.32	9.557%	$263.2874	$263.29	$263.30	$263.30
Purchase #7	$14.25	8.156%	$15.4122	$15.41	$15.40	$15.40
7 purchase totals =	$859.13		$944.9440	$944.95	$944.95	$944.90