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	$55.46	9.508%	$60.7331	$60.73	$60.75	$60.70
Purchase #2	$114.98	12.510%	$129.364	$129.36	$129.35	$129.40
Purchase #3	$156.60	7.438%	$168.2479	$168.25	$168.25	$168.20
Purchase #4	$92.79	13.326%	$105.1552	$105.16	$105.15	$105.20
Purchase #5	$27.58	5.270%	$29.0335	$29.03	$29.05	$29.00
Purchase #6	$119.31	3.517%	$123.5061	$123.51	$123.50	$123.50
Purchase #7	$100.72	7.711%	$108.4865	$108.49	$108.50	$108.50
7 purchase totals =	$667.44		$724.5263	$724.53	$724.55	$724.50