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	$38.70	4.737%	$40.5332	$40.53	$40.55	$40.50
Purchase #2	$135.33	4.560%	$141.501	$141.50	$141.50	$141.50
Purchase #3	$89.52	6.190%	$95.0613	$95.06	$95.05	$95.10
Purchase #4	$246.53	4.603%	$257.8778	$257.88	$257.90	$257.90
Purchase #5	$127.55	7.503%	$137.1201	$137.12	$137.10	$137.10
Purchase #6	$235.98	11.284%	$262.608	$262.61	$262.60	$262.60
Purchase #7	$73.64	5.353%	$77.5819	$77.58	$77.60	$77.60
7 purchase totals =	$947.25		$1,012.2833	$1,012.28	$1,012.30	$1,012.30