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	$201.30	13.506%	$228.4876	$228.49	$228.50	$228.50
Purchase #2	$85.77	5.304%	$90.3192	$90.32	$90.30	$90.30
Purchase #3	$67.57	6.253%	$71.7952	$71.80	$71.80	$71.80
Purchase #4	$136.73	10.316%	$150.8351	$150.84	$150.85	$150.80
Purchase #5	$82.29	11.703%	$91.9204	$91.92	$91.90	$91.90
Purchase #6	$125.59	4.516%	$131.2616	$131.26	$131.25	$131.30
Purchase #7	$228.80	3.513%	$236.8377	$236.84	$236.85	$236.80
7 purchase totals =	$928.05		$1,001.4568	$1,001.47	$1,001.45	$1,001.40