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	$236.78	13.727%	$269.2828	$269.28	$269.30	$269.30
Purchase #2	$29.88	13.216%	$33.8289	$33.83	$33.85	$33.80
Purchase #3	$207.84	6.786%	$221.944	$221.94	$221.95	$221.90
Purchase #4	$24.34	5.652%	$25.7157	$25.72	$25.70	$25.70
Purchase #5	$146.91	3.679%	$152.3148	$152.31	$152.30	$152.30
Purchase #6	$69.77	11.636%	$77.8884	$77.89	$77.90	$77.90
Purchase #7	$243.44	8.285%	$263.609	$263.61	$263.60	$263.60
7 purchase totals =	$958.96		$1,044.5836	$1,044.58	$1,044.60	$1,044.50