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	$237.34	4.371%	$247.7141	$247.71	$247.70	$247.70
Purchase #2	$232.56	4.481%	$242.981	$242.98	$243.00	$243.00
Purchase #3	$91.34	9.512%	$100.0283	$100.03	$100.05	$100.00
Purchase #4	$40.46	8.218%	$43.785	$43.79	$43.80	$43.80
Purchase #5	$131.72	11.254%	$146.5438	$146.54	$146.55	$146.50
Purchase #6	$151.56	8.831%	$164.9443	$164.94	$164.95	$164.90
Purchase #7	$66.28	3.449%	$68.566	$68.57	$68.55	$68.60
7 purchase totals =	$951.26		$1,014.5625	$1,014.56	$1,014.60	$1,014.50