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	$86.89	3.472%	$89.9068	$89.91	$89.90	$89.90
Purchase #2	$110.88	3.503%	$114.7641	$114.76	$114.75	$114.80
Purchase #3	$66.71	7.160%	$71.4864	$71.49	$71.50	$71.50
Purchase #4	$222.78	10.223%	$245.5548	$245.55	$245.55	$245.60
Purchase #5	$77.39	10.588%	$85.5841	$85.58	$85.60	$85.60
Purchase #6	$218.78	7.691%	$235.6064	$235.61	$235.60	$235.60
Purchase #7	$113.51	11.812%	$126.9178	$126.92	$126.90	$126.90
7 purchase totals =	$896.94		$969.8204	$969.82	$969.80	$969.90