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	$148.29	12.473%	$166.7862	$166.79	$166.80	$166.80
Purchase #2	$196.61	13.413%	$222.9813	$222.98	$223.00	$223.00
Purchase #3	$134.58	9.669%	$147.5925	$147.59	$147.60	$147.60
Purchase #4	$139.41	10.432%	$153.9533	$153.95	$153.95	$154.00
Purchase #5	$161.30	11.358%	$179.6205	$179.62	$179.60	$179.60
Purchase #6	$170.72	10.868%	$189.2738	$189.27	$189.25	$189.30
Purchase #7	$6.66	13.171%	$7.5372	$7.54	$7.55	$7.50
7 purchase totals =	$957.57		$1,067.7448	$1,067.74	$1,067.75	$1,067.80