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	$37.25	3.753%	$38.648	$38.65	$38.65	$38.60
Purchase #2	$83.74	3.576%	$86.7345	$86.73	$86.75	$86.70
Purchase #3	$225.29	3.313%	$232.7539	$232.75	$232.75	$232.80
Purchase #4	$136.50	7.444%	$146.6611	$146.66	$146.65	$146.70
Purchase #5	$176.91	11.229%	$196.7752	$196.78	$196.80	$196.80
Purchase #6	$52.98	12.175%	$59.4303	$59.43	$59.45	$59.40
Purchase #7	$238.50	4.859%	$250.0887	$250.09	$250.10	$250.10
7 purchase totals =	$951.17		$1,011.0917	$1,011.09	$1,011.15	$1,011.10