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	$33.86	6.741%	$36.1425	$36.14	$36.15	$36.10
Purchase #2	$87.72	7.643%	$94.4244	$94.42	$94.40	$94.40
Purchase #3	$9.59	7.530%	$10.3121	$10.31	$10.30	$10.30
Purchase #4	$166.78	4.117%	$173.6463	$173.65	$173.65	$173.60
Purchase #5	$178.80	9.807%	$196.3349	$196.33	$196.35	$196.30
Purchase #6	$124.41	4.711%	$130.271	$130.27	$130.25	$130.30
Purchase #7	$185.71	13.808%	$211.3528	$211.35	$211.35	$211.40
7 purchase totals =	$786.87		$852.4840	$852.47	$852.45	$852.40