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	$174.41	13.837%	$198.5431	$198.54	$198.55	$198.50
Purchase #2	$10.80	13.411%	$12.2484	$12.25	$12.25	$12.20
Purchase #3	$185.85	10.202%	$204.8104	$204.81	$204.80	$204.80
Purchase #4	$208.89	11.709%	$233.3489	$233.35	$233.35	$233.30
Purchase #5	$149.38	10.816%	$165.5369	$165.54	$165.55	$165.50
Purchase #6	$24.85	12.573%	$27.9744	$27.97	$27.95	$28.00
Purchase #7	$92.68	7.707%	$99.8228	$99.82	$99.80	$99.80
7 purchase totals =	$846.86		$942.2849	$942.28	$942.25	$942.10