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	$163.93	5.460%	$172.8806	$172.88	$172.90	$172.90
Purchase #2	$164.52	8.251%	$178.0945	$178.09	$178.10	$178.10
Purchase #3	$190.46	6.709%	$203.238	$203.24	$203.25	$203.20
Purchase #4	$179.81	8.620%	$195.3096	$195.31	$195.30	$195.30
Purchase #5	$158.53	5.307%	$166.9432	$166.94	$166.95	$166.90
Purchase #6	$53.79	11.217%	$59.8236	$59.82	$59.80	$59.80
Purchase #7	$97.64	7.465%	$104.9288	$104.93	$104.95	$104.90
7 purchase totals =	$1,008.68		$1,081.2183	$1,081.21	$1,081.25	$1,081.10