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	$54.66	9.119%	$59.6444	$59.64	$59.65	$59.60
Purchase #2	$142.74	8.729%	$155.1998	$155.20	$155.20	$155.20
Purchase #3	$190.85	3.191%	$196.94	$196.94	$196.95	$196.90
Purchase #4	$50.97	12.773%	$57.4804	$57.48	$57.50	$57.50
Purchase #5	$64.83	7.188%	$69.49	$69.49	$69.50	$69.50
Purchase #6	$55.33	8.135%	$59.8311	$59.83	$59.85	$59.80
Purchase #7	$136.61	8.178%	$147.782	$147.78	$147.80	$147.80
7 purchase totals =	$695.99		$746.3677	$746.36	$746.45	$746.30