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	$31.27	3.846%	$32.4726	$32.47	$32.45	$32.50
Purchase #2	$124.53	6.155%	$132.1948	$132.19	$132.20	$132.20
Purchase #3	$36.54	10.217%	$40.2733	$40.27	$40.25	$40.30
Purchase #4	$46.70	9.804%	$51.2785	$51.28	$51.30	$51.30
Purchase #5	$31.54	3.569%	$32.6657	$32.67	$32.65	$32.70
Purchase #6	$224.35	4.366%	$234.1451	$234.15	$234.15	$234.10
Purchase #7	$245.51	5.278%	$258.468	$258.47	$258.45	$258.50
7 purchase totals =	$740.44		$781.4980	$781.50	$781.45	$781.60