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	$194.73	8.658%	$211.5897	$211.59	$211.60	$211.60
Purchase #2	$239.33	6.615%	$255.1617	$255.16	$255.15	$255.20
Purchase #3	$142.90	4.616%	$149.4963	$149.50	$149.50	$149.50
Purchase #4	$87.66	3.166%	$90.4353	$90.44	$90.45	$90.40
Purchase #5	$82.46	6.355%	$87.7003	$87.70	$87.70	$87.70
Purchase #6	$184.50	3.747%	$191.4132	$191.41	$191.40	$191.40
Purchase #7	$128.63	10.317%	$141.9008	$141.90	$141.90	$141.90
7 purchase totals =	$1,060.21		$1,127.6973	$1,127.70	$1,127.70	$1,127.70