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	$156.57	12.364%	$175.9283	$175.93	$175.95	$175.90
Purchase #2	$154.70	3.615%	$160.2924	$160.29	$160.30	$160.30
Purchase #3	$126.67	13.607%	$143.906	$143.91	$143.90	$143.90
Purchase #4	$82.51	8.749%	$89.7288	$89.73	$89.75	$89.70
Purchase #5	$244.98	5.774%	$259.1251	$259.13	$259.15	$259.10
Purchase #6	$26.31	10.313%	$29.0234	$29.02	$29.00	$29.00
Purchase #7	$82.58	4.768%	$86.5174	$86.52	$86.50	$86.50
7 purchase totals =	$874.32		$944.5214	$944.53	$944.55	$944.40