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	$129.88	12.755%	$146.4462	$146.45	$146.45	$146.40
Purchase #2	$54.72	8.760%	$59.5135	$59.51	$59.50	$59.50
Purchase #3	$5.51	13.557%	$6.257	$6.26	$6.25	$6.30
Purchase #4	$20.78	9.611%	$22.7772	$22.78	$22.80	$22.80
Purchase #5	$128.25	12.648%	$144.4711	$144.47	$144.45	$144.50
Purchase #6	$237.39	11.471%	$264.621	$264.62	$264.60	$264.60
Purchase #7	$77.30	13.113%	$87.4363	$87.44	$87.45	$87.40
7 purchase totals =	$653.83		$731.5223	$731.53	$731.50	$731.50