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	$47.94	9.739%	$52.6089	$52.61	$52.60	$52.60
Purchase #2	$76.67	11.478%	$85.4702	$85.47	$85.45	$85.50
Purchase #3	$218.69	10.862%	$242.4441	$242.44	$242.45	$242.40
Purchase #4	$154.38	11.552%	$172.214	$172.21	$172.20	$172.20
Purchase #5	$197.53	3.566%	$204.5739	$204.57	$204.55	$204.60
Purchase #6	$129.51	12.660%	$145.906	$145.91	$145.90	$145.90
Purchase #7	$168.61	9.728%	$185.0124	$185.01	$185.00	$185.00
7 purchase totals =	$993.33		$1,088.2295	$1,088.22	$1,088.15	$1,088.20