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	$141.89	12.868%	$160.1484	$160.15	$160.15	$160.10
Purchase #2	$195.31	12.146%	$219.0324	$219.03	$219.05	$219.00
Purchase #3	$131.88	11.564%	$147.1306	$147.13	$147.15	$147.10
Purchase #4	$39.71	6.454%	$42.2729	$42.27	$42.25	$42.30
Purchase #5	$71.51	8.525%	$77.6062	$77.61	$77.60	$77.60
Purchase #6	$181.47	12.758%	$204.6219	$204.62	$204.60	$204.60
Purchase #7	$95.45	5.141%	$100.3571	$100.36	$100.35	$100.40
7 purchase totals =	$857.22		$951.1695	$951.17	$951.15	$951.10