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	$35.69	7.739%	$38.452	$38.45	$38.45	$38.50
Purchase #2	$81.63	9.839%	$89.6616	$89.66	$89.65	$89.70
Purchase #3	$87.99	8.595%	$95.5527	$95.55	$95.55	$95.60
Purchase #4	$233.34	13.343%	$264.4746	$264.47	$264.45	$264.50
Purchase #5	$229.35	11.375%	$255.4386	$255.44	$255.45	$255.40
Purchase #6	$124.78	10.435%	$137.8008	$137.80	$137.80	$137.80
Purchase #7	$218.58	11.718%	$244.1932	$244.19	$244.20	$244.20
7 purchase totals =	$1,011.36		$1,125.5735	$1,125.56	$1,125.55	$1,125.70