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	$37.61	11.163%	$41.8084	$41.81	$41.80	$41.80
Purchase #2	$75.91	13.145%	$85.8884	$85.89	$85.90	$85.90
Purchase #3	$190.64	9.218%	$208.2132	$208.21	$208.20	$208.20
Purchase #4	$222.32	7.207%	$238.3426	$238.34	$238.35	$238.30
Purchase #5	$191.61	10.702%	$212.1161	$212.12	$212.10	$212.10
Purchase #6	$167.27	3.148%	$172.5357	$172.54	$172.55	$172.50
Purchase #7	$142.75	7.730%	$153.7846	$153.78	$153.80	$153.80
7 purchase totals =	$1,028.11		$1,112.6890	$1,112.69	$1,112.70	$1,112.60