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	$90.43	6.625%	$96.421	$96.42	$96.40	$96.40
Purchase #2	$114.31	10.684%	$126.5229	$126.52	$126.50	$126.50
Purchase #3	$238.53	11.183%	$265.2048	$265.20	$265.20	$265.20
Purchase #4	$237.59	11.762%	$265.5353	$265.54	$265.55	$265.50
Purchase #5	$171.54	6.622%	$182.8994	$182.90	$182.90	$182.90
Purchase #6	$60.29	12.784%	$67.9975	$68.00	$68.00	$68.00
Purchase #7	$88.59	3.837%	$91.9892	$91.99	$92.00	$92.00
7 purchase totals =	$1,001.28		$1,096.5701	$1,096.57	$1,096.55	$1,096.50