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	$173.45	4.840%	$181.845	$181.85	$181.85	$181.80
Purchase #2	$68.61	12.790%	$77.3852	$77.39	$77.40	$77.40
Purchase #3	$232.62	7.560%	$250.2061	$250.21	$250.20	$250.20
Purchase #4	$185.31	7.698%	$199.5752	$199.58	$199.60	$199.60
Purchase #5	$106.76	11.691%	$119.2413	$119.24	$119.25	$119.20
Purchase #6	$142.58	7.642%	$153.476	$153.48	$153.50	$153.50
Purchase #7	$93.45	6.846%	$99.8476	$99.85	$99.85	$99.80
7 purchase totals =	$1,002.78		$1,081.5764	$1,081.60	$1,081.65	$1,081.50