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	$104.48	11.460%	$116.4534	$116.45	$116.45	$116.50
Purchase #2	$71.86	9.231%	$78.4934	$78.49	$78.50	$78.50
Purchase #3	$221.34	5.511%	$233.538	$233.54	$233.55	$233.50
Purchase #4	$67.54	12.165%	$75.7562	$75.76	$75.75	$75.80
Purchase #5	$53.50	6.441%	$56.9459	$56.95	$56.95	$56.90
Purchase #6	$101.57	6.415%	$108.0857	$108.09	$108.10	$108.10
Purchase #7	$45.30	4.761%	$47.4567	$47.46	$47.45	$47.50
7 purchase totals =	$665.59		$716.7293	$716.74	$716.75	$716.80