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	$149.52	10.549%	$165.2929	$165.29	$165.30	$165.30
Purchase #2	$72.31	5.235%	$76.0954	$76.10	$76.10	$76.10
Purchase #3	$190.54	5.166%	$200.3833	$200.38	$200.40	$200.40
Purchase #4	$63.96	11.689%	$71.4363	$71.44	$71.45	$71.40
Purchase #5	$27.49	6.489%	$29.2738	$29.27	$29.25	$29.30
Purchase #6	$159.54	4.561%	$166.8166	$166.82	$166.80	$166.80
Purchase #7	$129.27	5.188%	$135.9765	$135.98	$136.00	$136.00
7 purchase totals =	$792.63		$845.2748	$845.28	$845.30	$845.30