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	$147.82	3.414%	$152.8666	$152.87	$152.85	$152.90
Purchase #2	$220.71	13.653%	$250.8435	$250.84	$250.85	$250.80
Purchase #3	$161.30	12.774%	$181.9045	$181.90	$181.90	$181.90
Purchase #4	$184.31	6.764%	$196.7767	$196.78	$196.80	$196.80
Purchase #5	$94.45	12.281%	$106.0494	$106.05	$106.05	$106.00
Purchase #6	$18.74	11.771%	$20.9459	$20.95	$20.95	$20.90
Purchase #7	$211.97	8.662%	$230.3308	$230.33	$230.35	$230.30
7 purchase totals =	$1,039.30		$1,139.7174	$1,139.72	$1,139.75	$1,139.60