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	$121.88	7.502%	$131.0234	$131.02	$131.00	$131.00
Purchase #2	$238.61	7.271%	$255.9593	$255.96	$255.95	$256.00
Purchase #3	$242.63	3.201%	$250.3966	$250.40	$250.40	$250.40
Purchase #4	$191.65	3.221%	$197.823	$197.82	$197.80	$197.80
Purchase #5	$209.60	4.712%	$219.4764	$219.48	$219.50	$219.50
Purchase #6	$145.80	8.653%	$158.4161	$158.42	$158.40	$158.40
Purchase #7	$172.90	10.602%	$191.2309	$191.23	$191.25	$191.20
7 purchase totals =	$1,323.07		$1,404.3257	$1,404.33	$1,404.30	$1,404.30