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	$74.80	5.145%	$78.6485	$78.65	$78.65	$78.60
Purchase #2	$123.72	6.518%	$131.7841	$131.78	$131.80	$131.80
Purchase #3	$64.89	3.404%	$67.0989	$67.10	$67.10	$67.10
Purchase #4	$79.48	8.635%	$86.3431	$86.34	$86.35	$86.30
Purchase #5	$119.62	3.287%	$123.5519	$123.55	$123.55	$123.60
Purchase #6	$38.95	5.378%	$41.0447	$41.04	$41.05	$41.00
Purchase #7	$197.75	13.617%	$224.6776	$224.68	$224.70	$224.70
7 purchase totals =	$699.21		$753.1488	$753.14	$753.20	$753.10