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	$135.30	6.223%	$143.7197	$143.72	$143.70	$143.70
Purchase #2	$67.39	6.792%	$71.9671	$71.97	$71.95	$72.00
Purchase #3	$43.59	7.112%	$46.6901	$46.69	$46.70	$46.70
Purchase #4	$152.43	12.398%	$171.3283	$171.33	$171.35	$171.30
Purchase #5	$164.38	6.131%	$174.4581	$174.46	$174.45	$174.50
Purchase #6	$80.33	11.429%	$89.5109	$89.51	$89.50	$89.50
Purchase #7	$236.57	6.245%	$251.3438	$251.34	$251.35	$251.30
7 purchase totals =	$879.99		$949.0180	$949.02	$949.00	$949.00