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	$137.52	10.464%	$151.9101	$151.91	$151.90	$151.90
Purchase #2	$144.54	7.296%	$155.0856	$155.09	$155.10	$155.10
Purchase #3	$50.34	8.326%	$54.5313	$54.53	$54.55	$54.50
Purchase #4	$48.66	7.352%	$52.2375	$52.24	$52.25	$52.20
Purchase #5	$88.45	8.407%	$95.886	$95.89	$95.90	$95.90
Purchase #6	$170.36	13.644%	$193.6039	$193.60	$193.60	$193.60
Purchase #7	$174.44	4.831%	$182.8672	$182.87	$182.85	$182.90
7 purchase totals =	$814.31		$886.1216	$886.13	$886.15	$886.10