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	$238.61	3.777%	$247.6223	$247.62	$247.60	$247.60
Purchase #2	$213.49	9.367%	$233.4876	$233.49	$233.50	$233.50
Purchase #3	$88.59	12.104%	$99.3129	$99.31	$99.30	$99.30
Purchase #4	$138.39	5.673%	$146.2409	$146.24	$146.25	$146.20
Purchase #5	$163.76	5.542%	$172.8356	$172.84	$172.85	$172.80
Purchase #6	$108.83	9.513%	$119.183	$119.18	$119.20	$119.20
Purchase #7	$22.51	6.188%	$23.9029	$23.90	$23.90	$23.90
7 purchase totals =	$974.18		$1,042.5852	$1,042.58	$1,042.60	$1,042.50