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	$115.96	5.501%	$122.339	$122.34	$122.35	$122.30
Purchase #2	$69.87	12.460%	$78.5758	$78.58	$78.60	$78.60
Purchase #3	$160.29	3.233%	$165.4722	$165.47	$165.45	$165.50
Purchase #4	$204.30	10.489%	$225.729	$225.73	$225.75	$225.70
Purchase #5	$124.95	10.121%	$137.5962	$137.60	$137.60	$137.60
Purchase #6	$73.90	11.189%	$82.1687	$82.17	$82.15	$82.20
Purchase #7	$131.54	7.839%	$141.8514	$141.85	$141.85	$141.90
7 purchase totals =	$880.81		$953.7323	$953.74	$953.75	$953.80