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	$79.51	11.398%	$88.5725	$88.57	$88.55	$88.60
Purchase #2	$72.93	6.295%	$77.5209	$77.52	$77.50	$77.50
Purchase #3	$139.83	8.423%	$151.6079	$151.61	$151.60	$151.60
Purchase #4	$173.38	12.462%	$194.9866	$194.99	$195.00	$195.00
Purchase #5	$204.71	12.144%	$229.57	$229.57	$229.55	$229.60
Purchase #6	$172.79	13.531%	$196.1702	$196.17	$196.15	$196.20
Purchase #7	$74.95	5.271%	$78.9006	$78.90	$78.90	$78.90
7 purchase totals =	$918.10		$1,017.3287	$1,017.33	$1,017.25	$1,017.40