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	$89.93	13.324%	$101.9123	$101.91	$101.90	$101.90
Purchase #2	$123.63	10.749%	$136.919	$136.92	$136.90	$136.90
Purchase #3	$9.78	9.561%	$10.7151	$10.72	$10.70	$10.70
Purchase #4	$212.33	12.501%	$238.8734	$238.87	$238.85	$238.90
Purchase #5	$250.25	9.618%	$274.319	$274.32	$274.30	$274.30
Purchase #6	$183.96	7.759%	$198.2335	$198.23	$198.25	$198.20
Purchase #7	$58.34	3.671%	$60.4817	$60.48	$60.50	$60.50
7 purchase totals =	$928.22		$1,021.4540	$1,021.45	$1,021.40	$1,021.40