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	$112.38	4.621%	$117.5731	$117.57	$117.55	$117.60
Purchase #2	$85.41	12.707%	$96.263	$96.26	$96.25	$96.30
Purchase #3	$117.66	9.448%	$128.7765	$128.78	$128.80	$128.80
Purchase #4	$229.26	11.628%	$255.9184	$255.92	$255.90	$255.90
Purchase #5	$79.61	13.741%	$90.5492	$90.55	$90.55	$90.50
Purchase #6	$177.52	12.810%	$200.2603	$200.26	$200.25	$200.30
Purchase #7	$10.50	4.126%	$10.9332	$10.93	$10.95	$10.90
7 purchase totals =	$812.34		$900.2737	$900.27	$900.25	$900.30