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	$229.82	12.321%	$258.1361	$258.14	$258.15	$258.10
Purchase #2	$7.77	13.526%	$8.821	$8.82	$8.80	$8.80
Purchase #3	$142.39	5.483%	$150.1972	$150.20	$150.20	$150.20
Purchase #4	$75.96	8.313%	$82.2746	$82.27	$82.25	$82.30
Purchase #5	$233.76	10.505%	$258.3165	$258.32	$258.30	$258.30
Purchase #6	$53.26	13.659%	$60.5348	$60.53	$60.55	$60.50
Purchase #7	$230.26	5.814%	$243.6473	$243.65	$243.65	$243.60
7 purchase totals =	$973.22		$1,061.9275	$1,061.93	$1,061.90	$1,061.80