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	$114.52	13.482%	$129.9596	$129.96	$129.95	$130.00
Purchase #2	$52.83	6.447%	$56.236	$56.24	$56.25	$56.20
Purchase #3	$155.39	7.136%	$166.4786	$166.48	$166.50	$166.50
Purchase #4	$178.36	9.510%	$195.322	$195.32	$195.30	$195.30
Purchase #5	$48.81	5.131%	$51.3144	$51.31	$51.30	$51.30
Purchase #6	$57.89	3.191%	$59.7373	$59.74	$59.75	$59.70
Purchase #7	$58.79	10.213%	$64.7942	$64.79	$64.80	$64.80
7 purchase totals =	$666.59		$723.8421	$723.84	$723.85	$723.80