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	$149.64	3.252%	$154.5063	$154.51	$154.50	$154.50
Purchase #2	$57.50	7.596%	$61.8677	$61.87	$61.85	$61.90
Purchase #3	$55.48	10.810%	$61.4774	$61.48	$61.50	$61.50
Purchase #4	$224.72	10.381%	$248.0482	$248.05	$248.05	$248.00
Purchase #5	$98.39	5.156%	$103.463	$103.46	$103.45	$103.50
Purchase #6	$81.48	8.127%	$88.1019	$88.10	$88.10	$88.10
Purchase #7	$76.95	4.617%	$80.5028	$80.50	$80.50	$80.50
7 purchase totals =	$744.16		$797.9673	$797.97	$797.95	$798.00