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	$116.31	11.249%	$129.3937	$129.39	$129.40	$129.40
Purchase #2	$89.92	5.685%	$95.032	$95.03	$95.05	$95.00
Purchase #3	$127.89	10.688%	$141.5589	$141.56	$141.55	$141.60
Purchase #4	$113.37	6.299%	$120.5112	$120.51	$120.50	$120.50
Purchase #5	$145.50	13.700%	$165.4335	$165.43	$165.45	$165.40
Purchase #6	$144.89	3.834%	$150.4451	$150.45	$150.45	$150.40
Purchase #7	$87.77	8.264%	$95.0233	$95.02	$95.00	$95.00
7 purchase totals =	$825.65		$897.3977	$897.39	$897.40	$897.30