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	$225.36	9.405%	$246.5551	$246.56	$246.55	$246.60
Purchase #2	$111.75	4.216%	$116.4614	$116.46	$116.45	$116.50
Purchase #3	$121.46	7.712%	$130.827	$130.83	$130.85	$130.80
Purchase #4	$241.96	3.488%	$250.3996	$250.40	$250.40	$250.40
Purchase #5	$131.84	5.554%	$139.1624	$139.16	$139.15	$139.20
Purchase #6	$235.62	8.180%	$254.8937	$254.89	$254.90	$254.90
Purchase #7	$46.72	13.367%	$52.9651	$52.97	$52.95	$53.00
7 purchase totals =	$1,114.71		$1,191.2643	$1,191.27	$1,191.25	$1,191.40