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	$59.66	4.568%	$62.3853	$62.39	$62.40	$62.40
Purchase #2	$138.89	4.680%	$145.3901	$145.39	$145.40	$145.40
Purchase #3	$205.97	9.639%	$225.8234	$225.82	$225.80	$225.80
Purchase #4	$157.48	4.845%	$165.1099	$165.11	$165.10	$165.10
Purchase #5	$243.35	4.456%	$254.1937	$254.19	$254.20	$254.20
Purchase #6	$52.85	6.518%	$56.2948	$56.29	$56.30	$56.30
Purchase #7	$145.60	7.201%	$156.0847	$156.08	$156.10	$156.10
7 purchase totals =	$1,003.80		$1,065.2819	$1,065.27	$1,065.30	$1,065.30