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	$71.33	6.190%	$75.7453	$75.75	$75.75	$75.70
Purchase #2	$185.63	5.819%	$196.4318	$196.43	$196.45	$196.40
Purchase #3	$230.51	10.718%	$255.2161	$255.22	$255.20	$255.20
Purchase #4	$189.78	10.848%	$210.3673	$210.37	$210.35	$210.40
Purchase #5	$203.75	9.408%	$222.9188	$222.92	$222.90	$222.90
Purchase #6	$94.61	12.249%	$106.1988	$106.20	$106.20	$106.20
Purchase #7	$87.34	12.279%	$98.0645	$98.06	$98.05	$98.10
7 purchase totals =	$1,062.95		$1,164.9426	$1,164.95	$1,164.90	$1,164.90