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	$187.27	12.821%	$211.2799	$211.28	$211.30	$211.30
Purchase #2	$58.47	5.222%	$61.5233	$61.52	$61.50	$61.50
Purchase #3	$143.37	12.271%	$160.9629	$160.96	$160.95	$161.00
Purchase #4	$114.47	8.172%	$123.8245	$123.82	$123.80	$123.80
Purchase #5	$141.52	8.102%	$152.986	$152.99	$153.00	$153.00
Purchase #6	$165.75	11.548%	$184.8908	$184.89	$184.90	$184.90
Purchase #7	$72.33	8.149%	$78.2242	$78.22	$78.20	$78.20
7 purchase totals =	$883.18		$973.6916	$973.68	$973.65	$973.70