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	$158.89	8.538%	$172.456	$172.46	$172.45	$172.50
Purchase #2	$26.52	7.456%	$28.4973	$28.50	$28.50	$28.50
Purchase #3	$195.76	3.472%	$202.5568	$202.56	$202.55	$202.60
Purchase #4	$160.72	9.461%	$175.9257	$175.93	$175.95	$175.90
Purchase #5	$67.53	13.855%	$76.8863	$76.89	$76.90	$76.90
Purchase #6	$61.77	8.469%	$67.0013	$67.00	$67.00	$67.00
Purchase #7	$89.57	7.371%	$96.1722	$96.17	$96.15	$96.20
7 purchase totals =	$760.76		$819.4956	$819.51	$819.50	$819.60