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	$137.61	10.716%	$152.3563	$152.36	$152.35	$152.40
Purchase #2	$51.78	7.345%	$55.5832	$55.58	$55.60	$55.60
Purchase #3	$137.82	11.295%	$153.3868	$153.39	$153.40	$153.40
Purchase #4	$210.38	12.846%	$237.4054	$237.41	$237.40	$237.40
Purchase #5	$50.62	11.400%	$56.3907	$56.39	$56.40	$56.40
Purchase #6	$22.32	8.502%	$24.2176	$24.22	$24.20	$24.20
Purchase #7	$111.33	10.798%	$123.3514	$123.35	$123.35	$123.40
7 purchase totals =	$721.86		$802.6914	$802.70	$802.70	$802.80