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	$191.89	6.872%	$205.0767	$205.08	$205.10	$205.10
Purchase #2	$126.25	8.810%	$137.3726	$137.37	$137.35	$137.40
Purchase #3	$155.55	9.834%	$170.8468	$170.85	$170.85	$170.80
Purchase #4	$200.33	8.110%	$216.5768	$216.58	$216.60	$216.60
Purchase #5	$61.39	7.344%	$65.8985	$65.90	$65.90	$65.90
Purchase #6	$72.30	13.618%	$82.1458	$82.15	$82.15	$82.10
Purchase #7	$153.46	7.604%	$165.1291	$165.13	$165.15	$165.10
7 purchase totals =	$961.17		$1,043.0463	$1,043.06	$1,043.10	$1,043.00