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	$151.75	6.472%	$161.5713	$161.57	$161.55	$161.60
Purchase #2	$176.96	13.317%	$200.5258	$200.53	$200.55	$200.50
Purchase #3	$195.97	13.423%	$222.2751	$222.28	$222.30	$222.30
Purchase #4	$203.74	13.830%	$231.9172	$231.92	$231.90	$231.90
Purchase #5	$73.48	11.325%	$81.8016	$81.80	$81.80	$81.80
Purchase #6	$236.34	5.121%	$248.443	$248.44	$248.45	$248.40
Purchase #7	$33.37	12.708%	$37.6107	$37.61	$37.60	$37.60
7 purchase totals =	$1,071.61		$1,184.1447	$1,184.15	$1,184.15	$1,184.10