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	$66.89	8.847%	$72.8078	$72.81	$72.80	$72.80
Purchase #2	$249.77	10.145%	$275.1092	$275.11	$275.10	$275.10
Purchase #3	$168.58	4.663%	$176.4409	$176.44	$176.45	$176.40
Purchase #4	$242.87	9.817%	$266.7125	$266.71	$266.70	$266.70
Purchase #5	$59.59	10.630%	$65.9244	$65.92	$65.90	$65.90
Purchase #6	$33.87	6.622%	$36.1129	$36.11	$36.10	$36.10
Purchase #7	$235.81	12.569%	$265.449	$265.45	$265.45	$265.40
7 purchase totals =	$1,057.38		$1,158.5567	$1,158.55	$1,158.50	$1,158.40