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	$151.97	3.613%	$157.4607	$157.46	$157.45	$157.50
Purchase #2	$159.57	12.654%	$179.762	$179.76	$179.75	$179.80
Purchase #3	$98.74	12.784%	$111.3629	$111.36	$111.35	$111.40
Purchase #4	$245.77	10.779%	$272.2615	$272.26	$272.25	$272.30
Purchase #5	$169.96	11.738%	$189.9099	$189.91	$189.90	$189.90
Purchase #6	$216.66	12.576%	$243.9072	$243.91	$243.90	$243.90
Purchase #7	$164.42	12.362%	$184.7456	$184.75	$184.75	$184.70
7 purchase totals =	$1,207.09		$1,339.4098	$1,339.41	$1,339.35	$1,339.50