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	$10.52	7.712%	$11.3313	$11.33	$11.35	$11.30
Purchase #2	$56.83	10.322%	$62.696	$62.70	$62.70	$62.70
Purchase #3	$244.31	5.612%	$258.0207	$258.02	$258.00	$258.00
Purchase #4	$82.90	10.261%	$91.4064	$91.41	$91.40	$91.40
Purchase #5	$45.59	10.617%	$50.4303	$50.43	$50.45	$50.40
Purchase #6	$84.56	13.253%	$95.7667	$95.77	$95.75	$95.80
Purchase #7	$199.58	11.187%	$221.907	$221.91	$221.90	$221.90
7 purchase totals =	$724.29		$791.5584	$791.57	$791.55	$791.50