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	$36.29	3.460%	$37.5456	$37.55	$37.55	$37.50
Purchase #2	$66.32	5.832%	$70.1878	$70.19	$70.20	$70.20
Purchase #3	$115.72	12.501%	$130.1862	$130.19	$130.20	$130.20
Purchase #4	$124.45	13.798%	$141.6216	$141.62	$141.60	$141.60
Purchase #5	$114.35	4.869%	$119.9177	$119.92	$119.90	$119.90
Purchase #6	$99.49	13.843%	$113.2624	$113.26	$113.25	$113.30
Purchase #7	$114.37	11.732%	$127.7879	$127.79	$127.80	$127.80
7 purchase totals =	$670.99		$740.5092	$740.52	$740.50	$740.50