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	$44.92	3.813%	$46.6328	$46.63	$46.65	$46.60
Purchase #2	$52.67	7.379%	$56.5565	$56.56	$56.55	$56.60
Purchase #3	$88.92	13.458%	$100.8869	$100.89	$100.90	$100.90
Purchase #4	$122.96	13.459%	$139.5092	$139.51	$139.50	$139.50
Purchase #5	$50.92	9.168%	$55.5883	$55.59	$55.60	$55.60
Purchase #6	$95.31	9.841%	$104.6895	$104.69	$104.70	$104.70
Purchase #7	$30.51	3.494%	$31.576	$31.58	$31.60	$31.60
7 purchase totals =	$486.21		$535.4392	$535.45	$535.50	$535.50