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	$100.95	7.107%	$108.1245	$108.12	$108.10	$108.10
Purchase #2	$32.91	13.301%	$37.2874	$37.29	$37.30	$37.30
Purchase #3	$185.71	10.390%	$205.0053	$205.01	$205.00	$205.00
Purchase #4	$53.49	8.328%	$57.9446	$57.94	$57.95	$57.90
Purchase #5	$193.34	3.199%	$199.5249	$199.52	$199.50	$199.50
Purchase #6	$27.50	13.418%	$31.19	$31.19	$31.20	$31.20
Purchase #7	$55.41	7.717%	$59.686	$59.69	$59.70	$59.70
7 purchase totals =	$649.31		$698.7627	$698.76	$698.75	$698.70