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	$48.33	10.791%	$53.5453	$53.55	$53.55	$53.50
Purchase #2	$30.67	3.654%	$31.7907	$31.79	$31.80	$31.80
Purchase #3	$144.86	4.705%	$151.6757	$151.68	$151.70	$151.70
Purchase #4	$240.36	6.247%	$255.3753	$255.38	$255.40	$255.40
Purchase #5	$98.40	4.223%	$102.5554	$102.56	$102.55	$102.60
Purchase #6	$112.63	6.778%	$120.2641	$120.26	$120.25	$120.30
Purchase #7	$237.34	5.711%	$250.8945	$250.89	$250.90	$250.90
7 purchase totals =	$912.59		$966.1010	$966.11	$966.15	$966.20