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	$95.61	7.746%	$103.016	$103.02	$103.00	$103.00
Purchase #2	$60.76	11.621%	$67.8209	$67.82	$67.80	$67.80
Purchase #3	$120.26	11.822%	$134.4771	$134.48	$134.50	$134.50
Purchase #4	$178.42	11.493%	$198.9258	$198.93	$198.95	$198.90
Purchase #5	$35.44	11.727%	$39.596	$39.60	$39.60	$39.60
Purchase #6	$245.76	13.339%	$278.5419	$278.54	$278.55	$278.50
Purchase #7	$149.48	6.401%	$159.0482	$159.05	$159.05	$159.00
7 purchase totals =	$885.73		$981.4259	$981.44	$981.45	$981.30