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	$52.79	4.709%	$55.2759	$55.28	$55.30	$55.30
Purchase #2	$35.63	6.204%	$37.8405	$37.84	$37.85	$37.80
Purchase #3	$106.38	11.343%	$118.4467	$118.45	$118.45	$118.40
Purchase #4	$145.43	7.733%	$156.6761	$156.68	$156.70	$156.70
Purchase #5	$141.97	11.807%	$158.7324	$158.73	$158.75	$158.70
Purchase #6	$245.72	4.399%	$256.5292	$256.53	$256.55	$256.50
Purchase #7	$110.86	6.318%	$117.8641	$117.86	$117.85	$117.90
7 purchase totals =	$838.78		$901.3649	$901.37	$901.45	$901.30