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	$215.91	3.221%	$222.8645	$222.86	$222.85	$222.90
Purchase #2	$35.94	13.486%	$40.7869	$40.79	$40.80	$40.80
Purchase #3	$247.57	5.775%	$261.8672	$261.87	$261.85	$261.90
Purchase #4	$49.58	9.821%	$54.4493	$54.45	$54.45	$54.40
Purchase #5	$241.38	11.764%	$269.7759	$269.78	$269.80	$269.80
Purchase #6	$250.58	12.491%	$281.8799	$281.88	$281.90	$281.90
Purchase #7	$70.86	9.707%	$77.7384	$77.74	$77.75	$77.70
7 purchase totals =	$1,111.82		$1,209.3621	$1,209.37	$1,209.40	$1,209.40