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	$46.69	11.455%	$52.0383	$52.04	$52.05	$52.00
Purchase #2	$130.72	7.801%	$140.9175	$140.92	$140.90	$140.90
Purchase #3	$66.89	8.804%	$72.779	$72.78	$72.80	$72.80
Purchase #4	$101.41	7.505%	$109.0208	$109.02	$109.00	$109.00
Purchase #5	$26.87	9.740%	$29.4871	$29.49	$29.50	$29.50
Purchase #6	$127.72	13.353%	$144.7745	$144.77	$144.75	$144.80
Purchase #7	$135.75	8.605%	$147.4313	$147.43	$147.45	$147.40
7 purchase totals =	$636.05		$696.4485	$696.45	$696.45	$696.40