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	$185.59	7.405%	$199.3329	$199.33	$199.35	$199.30
Purchase #2	$54.36	9.775%	$59.6737	$59.67	$59.65	$59.70
Purchase #3	$98.85	4.413%	$103.2123	$103.21	$103.20	$103.20
Purchase #4	$173.68	9.824%	$190.7423	$190.74	$190.75	$190.70
Purchase #5	$216.99	8.236%	$234.8613	$234.86	$234.85	$234.90
Purchase #6	$67.47	5.646%	$71.2794	$71.28	$71.30	$71.30
Purchase #7	$211.90	7.325%	$227.4217	$227.42	$227.40	$227.40
7 purchase totals =	$1,008.84		$1,086.5236	$1,086.51	$1,086.50	$1,086.50