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	$141.75	9.867%	$155.7365	$155.74	$155.75	$155.70
Purchase #2	$87.25	12.450%	$98.1126	$98.11	$98.10	$98.10
Purchase #3	$216.61	13.785%	$246.4697	$246.47	$246.45	$246.50
Purchase #4	$94.34	3.445%	$97.59	$97.59	$97.60	$97.60
Purchase #5	$156.50	9.630%	$171.571	$171.57	$171.55	$171.60
Purchase #6	$39.84	9.399%	$43.5846	$43.58	$43.60	$43.60
Purchase #7	$168.87	12.819%	$190.5174	$190.52	$190.50	$190.50
7 purchase totals =	$905.16		$1,003.5818	$1,003.58	$1,003.55	$1,003.60