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	$143.54	4.229%	$149.6103	$149.61	$149.60	$149.60
Purchase #2	$229.30	7.208%	$245.8279	$245.83	$245.85	$245.80
Purchase #3	$209.62	4.695%	$219.4617	$219.46	$219.45	$219.50
Purchase #4	$112.75	6.769%	$120.382	$120.38	$120.40	$120.40
Purchase #5	$203.49	11.627%	$227.1498	$227.15	$227.15	$227.10
Purchase #6	$100.92	12.218%	$113.2504	$113.25	$113.25	$113.30
Purchase #7	$145.71	4.146%	$151.7511	$151.75	$151.75	$151.80
7 purchase totals =	$1,145.33		$1,227.4332	$1,227.43	$1,227.45	$1,227.50