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	$149.75	4.532%	$156.5367	$156.54	$156.55	$156.50
Purchase #2	$151.79	11.702%	$169.5525	$169.55	$169.55	$169.60
Purchase #3	$61.40	9.594%	$67.2907	$67.29	$67.30	$67.30
Purchase #4	$73.65	12.493%	$82.8511	$82.85	$82.85	$82.90
Purchase #5	$100.37	9.272%	$109.6763	$109.68	$109.70	$109.70
Purchase #6	$122.65	12.379%	$137.8328	$137.83	$137.85	$137.80
Purchase #7	$44.79	9.709%	$49.1387	$49.14	$49.15	$49.10
7 purchase totals =	$704.40		$772.8788	$772.88	$772.95	$772.90