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	$89.42	12.794%	$100.8604	$100.86	$100.85	$100.90
Purchase #2	$89.66	12.569%	$100.9294	$100.93	$100.95	$100.90
Purchase #3	$121.99	6.674%	$130.1316	$130.13	$130.15	$130.10
Purchase #4	$185.56	9.710%	$203.5779	$203.58	$203.60	$203.60
Purchase #5	$152.57	10.861%	$169.1406	$169.14	$169.15	$169.10
Purchase #6	$219.78	7.358%	$235.9514	$235.95	$235.95	$236.00
Purchase #7	$195.89	8.139%	$211.8335	$211.83	$211.85	$211.80
7 purchase totals =	$1,054.87		$1,152.4248	$1,152.42	$1,152.50	$1,152.40