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	$206.29	11.273%	$229.5451	$229.55	$229.55	$229.50
Purchase #2	$213.88	4.119%	$222.6897	$222.69	$222.70	$222.70
Purchase #3	$167.72	13.197%	$189.854	$189.85	$189.85	$189.90
Purchase #4	$40.67	3.749%	$42.1947	$42.19	$42.20	$42.20
Purchase #5	$97.71	8.803%	$106.3114	$106.31	$106.30	$106.30
Purchase #6	$148.72	10.511%	$164.352	$164.35	$164.35	$164.40
Purchase #7	$209.73	12.379%	$235.6925	$235.69	$235.70	$235.70
7 purchase totals =	$1,084.72		$1,190.6394	$1,190.63	$1,190.65	$1,190.70