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	$181.43	4.514%	$189.6198	$189.62	$189.60	$189.60
Purchase #2	$33.32	12.169%	$37.3747	$37.37	$37.35	$37.40
Purchase #3	$99.95	3.600%	$103.5482	$103.55	$103.55	$103.50
Purchase #4	$7.63	13.445%	$8.6559	$8.66	$8.65	$8.70
Purchase #5	$92.60	3.434%	$95.7799	$95.78	$95.80	$95.80
Purchase #6	$92.98	3.364%	$96.1078	$96.11	$96.10	$96.10
Purchase #7	$164.43	9.694%	$180.3698	$180.37	$180.35	$180.40
7 purchase totals =	$672.34		$711.4561	$711.46	$711.40	$711.50