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	$119.76	6.758%	$127.8534	$127.85	$127.85	$127.90
Purchase #2	$177.40	9.407%	$194.088	$194.09	$194.10	$194.10
Purchase #3	$147.31	12.653%	$165.9491	$165.95	$165.95	$165.90
Purchase #4	$155.33	9.495%	$170.0786	$170.08	$170.10	$170.10
Purchase #5	$59.66	11.647%	$66.6086	$66.61	$66.60	$66.60
Purchase #6	$174.98	7.235%	$187.6398	$187.64	$187.65	$187.60
Purchase #7	$152.67	13.244%	$172.8896	$172.89	$172.90	$172.90
7 purchase totals =	$987.11		$1,085.1071	$1,085.11	$1,085.15	$1,085.10