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	$92.79	11.689%	$103.6362	$103.64	$103.65	$103.60
Purchase #2	$81.72	4.420%	$85.332	$85.33	$85.35	$85.30
Purchase #3	$68.88	3.246%	$71.1158	$71.12	$71.10	$71.10
Purchase #4	$71.80	8.484%	$77.8915	$77.89	$77.90	$77.90
Purchase #5	$190.75	6.282%	$202.7329	$202.73	$202.75	$202.70
Purchase #6	$127.27	3.635%	$131.8963	$131.90	$131.90	$131.90
Purchase #7	$223.75	13.171%	$253.2201	$253.22	$253.20	$253.20
7 purchase totals =	$856.96		$925.8248	$925.83	$925.85	$925.70