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	$163.68	13.376%	$185.5738	$185.57	$185.55	$185.60
Purchase #2	$54.37	10.306%	$59.9734	$59.97	$59.95	$60.00
Purchase #3	$77.56	6.496%	$82.5983	$82.60	$82.60	$82.60
Purchase #4	$197.45	8.371%	$213.9785	$213.98	$214.00	$214.00
Purchase #5	$44.66	10.595%	$49.3917	$49.39	$49.40	$49.40
Purchase #6	$241.38	3.796%	$250.5428	$250.54	$250.55	$250.50
Purchase #7	$81.81	9.528%	$89.6049	$89.60	$89.60	$89.60
7 purchase totals =	$860.91		$931.6634	$931.65	$931.65	$931.70