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	$144.48	4.624%	$151.1608	$151.16	$151.15	$151.20
Purchase #2	$219.34	11.214%	$243.9368	$243.94	$243.95	$243.90
Purchase #3	$81.63	4.722%	$85.4846	$85.48	$85.50	$85.50
Purchase #4	$157.48	3.484%	$162.9666	$162.97	$162.95	$163.00
Purchase #5	$77.89	6.687%	$83.0985	$83.10	$83.10	$83.10
Purchase #6	$113.43	12.467%	$127.5713	$127.57	$127.55	$127.60
Purchase #7	$168.98	5.568%	$178.3888	$178.39	$178.40	$178.40
7 purchase totals =	$963.23		$1,032.6074	$1,032.61	$1,032.60	$1,032.70