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	$149.34	13.480%	$169.471	$169.47	$169.45	$169.50
Purchase #2	$69.67	12.809%	$78.594	$78.59	$78.60	$78.60
Purchase #3	$42.43	7.335%	$45.5422	$45.54	$45.55	$45.50
Purchase #4	$231.67	7.792%	$249.7217	$249.72	$249.70	$249.70
Purchase #5	$165.73	3.202%	$171.0367	$171.04	$171.05	$171.00
Purchase #6	$249.99	12.290%	$280.7138	$280.71	$280.70	$280.70
Purchase #7	$147.61	13.378%	$167.3573	$167.36	$167.35	$167.40
7 purchase totals =	$1,056.44		$1,162.4367	$1,162.43	$1,162.40	$1,162.40