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	$77.34	11.861%	$86.5133	$86.51	$86.50	$86.50
Purchase #2	$243.55	4.839%	$255.3354	$255.34	$255.35	$255.30
Purchase #3	$56.67	4.827%	$59.4055	$59.41	$59.40	$59.40
Purchase #4	$100.51	6.399%	$106.9416	$106.94	$106.95	$106.90
Purchase #5	$9.25	12.368%	$10.394	$10.39	$10.40	$10.40
Purchase #6	$7.78	6.551%	$8.2897	$8.29	$8.30	$8.30
Purchase #7	$101.89	4.457%	$106.4312	$106.43	$106.45	$106.40
7 purchase totals =	$596.99		$633.3107	$633.31	$633.35	$633.20