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	$191.33	4.427%	$199.8002	$199.80	$199.80	$199.80
Purchase #2	$236.59	7.228%	$253.6907	$253.69	$253.70	$253.70
Purchase #3	$161.47	5.565%	$170.4558	$170.46	$170.45	$170.50
Purchase #4	$74.75	10.364%	$82.4971	$82.50	$82.50	$82.50
Purchase #5	$57.34	3.633%	$59.4232	$59.42	$59.40	$59.40
Purchase #6	$110.92	11.495%	$123.6703	$123.67	$123.65	$123.70
Purchase #7	$248.75	6.282%	$264.3765	$264.38	$264.40	$264.40
7 purchase totals =	$1,081.15		$1,153.9138	$1,153.92	$1,153.90	$1,154.00