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	$146.28	3.593%	$151.5358	$151.54	$151.55	$151.50
Purchase #2	$60.65	11.336%	$67.5253	$67.53	$67.55	$67.50
Purchase #3	$37.59	11.372%	$41.8647	$41.86	$41.85	$41.90
Purchase #4	$142.56	6.551%	$151.8991	$151.90	$151.90	$151.90
Purchase #5	$128.25	7.715%	$138.1445	$138.14	$138.15	$138.10
Purchase #6	$145.29	5.703%	$153.5759	$153.58	$153.60	$153.60
Purchase #7	$175.52	5.551%	$185.2631	$185.26	$185.25	$185.30
7 purchase totals =	$836.14		$889.8084	$889.81	$889.85	$889.80