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	$231.86	6.323%	$246.5205	$246.52	$246.50	$246.50
Purchase #2	$237.59	3.339%	$245.5231	$245.52	$245.50	$245.50
Purchase #3	$157.87	4.109%	$164.3569	$164.36	$164.35	$164.40
Purchase #4	$219.37	12.151%	$246.0256	$246.03	$246.05	$246.00
Purchase #5	$124.51	13.502%	$141.3213	$141.32	$141.30	$141.30
Purchase #6	$143.88	5.482%	$151.7675	$151.77	$151.75	$151.80
Purchase #7	$179.41	6.131%	$190.4096	$190.41	$190.40	$190.40
7 purchase totals =	$1,294.49		$1,385.9245	$1,385.93	$1,385.85	$1,385.90