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	$190.60	12.785%	$214.9682	$214.97	$214.95	$215.00
Purchase #2	$240.52	13.575%	$273.1706	$273.17	$273.15	$273.20
Purchase #3	$191.39	10.702%	$211.8726	$211.87	$211.85	$211.90
Purchase #4	$67.26	13.231%	$76.1592	$76.16	$76.15	$76.20
Purchase #5	$68.64	3.804%	$71.2511	$71.25	$71.25	$71.30
Purchase #6	$139.88	8.279%	$151.4607	$151.46	$151.45	$151.50
Purchase #7	$40.76	6.504%	$43.411	$43.41	$43.40	$43.40
7 purchase totals =	$939.05		$1,042.2934	$1,042.29	$1,042.20	$1,042.50