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	$246.65	9.243%	$269.4479	$269.45	$269.45	$269.40
Purchase #2	$249.90	12.324%	$280.6977	$280.70	$280.70	$280.70
Purchase #3	$24.94	12.776%	$28.1263	$28.13	$28.15	$28.10
Purchase #4	$75.45	4.512%	$78.8543	$78.85	$78.85	$78.90
Purchase #5	$56.86	8.560%	$61.7272	$61.73	$61.75	$61.70
Purchase #6	$205.64	8.567%	$223.2572	$223.26	$223.25	$223.30
Purchase #7	$19.57	10.378%	$21.601	$21.60	$21.60	$21.60
7 purchase totals =	$879.01		$963.7116	$963.72	$963.75	$963.70