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	$172.38	8.811%	$187.5684	$187.57	$187.55	$187.60
Purchase #2	$61.82	8.432%	$67.0327	$67.03	$67.05	$67.00
Purchase #3	$56.47	11.688%	$63.0702	$63.07	$63.05	$63.10
Purchase #4	$169.72	7.406%	$182.2895	$182.29	$182.30	$182.30
Purchase #5	$91.51	8.816%	$99.5775	$99.58	$99.60	$99.60
Purchase #6	$147.46	7.794%	$158.953	$158.95	$158.95	$159.00
Purchase #7	$216.76	11.149%	$240.9266	$240.93	$240.95	$240.90
7 purchase totals =	$916.12		$999.4179	$999.42	$999.45	$999.50