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	$45.90	13.400%	$52.0506	$52.05	$52.05	$52.10
Purchase #2	$22.74	12.632%	$25.6125	$25.61	$25.60	$25.60
Purchase #3	$91.93	7.616%	$98.9314	$98.93	$98.95	$98.90
Purchase #4	$88.61	9.804%	$97.2973	$97.30	$97.30	$97.30
Purchase #5	$234.52	13.685%	$266.6141	$266.61	$266.60	$266.60
Purchase #6	$159.29	8.234%	$172.4059	$172.41	$172.40	$172.40
Purchase #7	$65.58	10.731%	$72.6174	$72.62	$72.60	$72.60
7 purchase totals =	$708.57		$785.5292	$785.53	$785.50	$785.50