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	$211.27	13.810%	$240.4464	$240.45	$240.45	$240.40
Purchase #2	$11.40	10.416%	$12.5874	$12.59	$12.60	$12.60
Purchase #3	$86.53	4.180%	$90.147	$90.15	$90.15	$90.10
Purchase #4	$154.39	7.171%	$165.4613	$165.46	$165.45	$165.50
Purchase #5	$168.61	12.276%	$189.3086	$189.31	$189.30	$189.30
Purchase #6	$133.78	8.125%	$144.6496	$144.65	$144.65	$144.60
Purchase #7	$88.29	4.545%	$92.3028	$92.30	$92.30	$92.30
7 purchase totals =	$854.27		$934.9031	$934.91	$934.90	$934.80