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	$122.88	9.644%	$134.7305	$134.73	$134.75	$134.70
Purchase #2	$184.80	13.872%	$210.4355	$210.44	$210.45	$210.40
Purchase #3	$167.91	11.519%	$187.2516	$187.25	$187.25	$187.30
Purchase #4	$40.35	8.505%	$43.7818	$43.78	$43.80	$43.80
Purchase #5	$193.39	11.260%	$215.1657	$215.17	$215.15	$215.20
Purchase #6	$49.51	10.414%	$54.666	$54.67	$54.65	$54.70
Purchase #7	$163.88	9.559%	$179.5453	$179.55	$179.55	$179.50
7 purchase totals =	$922.72		$1,025.5764	$1,025.59	$1,025.60	$1,025.60