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	$83.99	7.683%	$90.443	$90.44	$90.45	$90.40
Purchase #2	$216.51	3.618%	$224.3433	$224.34	$224.35	$224.30
Purchase #3	$240.74	3.304%	$248.694	$248.69	$248.70	$248.70
Purchase #4	$73.78	4.181%	$76.8647	$76.86	$76.85	$76.90
Purchase #5	$122.87	3.797%	$127.5354	$127.54	$127.55	$127.50
Purchase #6	$82.82	12.705%	$93.3423	$93.34	$93.35	$93.30
Purchase #7	$20.56	11.461%	$22.9164	$22.92	$22.90	$22.90
7 purchase totals =	$841.27		$884.1391	$884.13	$884.15	$884.00