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	$59.31	3.789%	$61.5573	$61.56	$61.55	$61.60
Purchase #2	$245.48	3.115%	$253.1267	$253.13	$253.15	$253.10
Purchase #3	$122.56	13.326%	$138.8923	$138.89	$138.90	$138.90
Purchase #4	$213.53	12.730%	$240.7124	$240.71	$240.70	$240.70
Purchase #5	$204.62	5.715%	$216.314	$216.31	$216.30	$216.30
Purchase #6	$10.81	5.327%	$11.3858	$11.39	$11.40	$11.40
Purchase #7	$214.52	4.318%	$223.783	$223.78	$223.80	$223.80
7 purchase totals =	$1,070.83		$1,145.7715	$1,145.77	$1,145.80	$1,145.80