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	$104.25	8.261%	$112.8621	$112.86	$112.85	$112.90
Purchase #2	$170.71	12.283%	$191.6783	$191.68	$191.70	$191.70
Purchase #3	$217.87	11.293%	$242.4741	$242.47	$242.45	$242.50
Purchase #4	$184.30	8.848%	$200.6069	$200.61	$200.60	$200.60
Purchase #5	$189.54	8.174%	$205.033	$205.03	$205.05	$205.00
Purchase #6	$53.72	12.148%	$60.2459	$60.25	$60.25	$60.20
Purchase #7	$91.98	4.559%	$96.1734	$96.17	$96.15	$96.20
7 purchase totals =	$1,012.37		$1,109.0737	$1,109.07	$1,109.05	$1,109.10