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	$91.90	9.597%	$100.7196	$100.72	$100.70	$100.70
Purchase #2	$114.77	4.825%	$120.3077	$120.31	$120.30	$120.30
Purchase #3	$81.75	4.850%	$85.7149	$85.71	$85.70	$85.70
Purchase #4	$208.92	9.674%	$229.1309	$229.13	$229.15	$229.10
Purchase #5	$143.92	6.141%	$152.7581	$152.76	$152.75	$152.80
Purchase #6	$241.58	3.770%	$250.6876	$250.69	$250.70	$250.70
Purchase #7	$13.33	11.504%	$14.8635	$14.86	$14.85	$14.90
7 purchase totals =	$896.17		$954.1823	$954.18	$954.15	$954.20