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	$101.49	11.702%	$113.3664	$113.37	$113.35	$113.40
Purchase #2	$141.78	6.333%	$150.7589	$150.76	$150.75	$150.80
Purchase #3	$93.96	9.862%	$103.2263	$103.23	$103.25	$103.20
Purchase #4	$168.53	6.747%	$179.9007	$179.90	$179.90	$179.90
Purchase #5	$154.73	6.771%	$165.2068	$165.21	$165.20	$165.20
Purchase #6	$206.59	11.563%	$230.478	$230.48	$230.50	$230.50
Purchase #7	$55.72	11.120%	$61.9161	$61.92	$61.90	$61.90
7 purchase totals =	$922.80		$1,004.8532	$1,004.87	$1,004.85	$1,004.90