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	$100.40	9.650%	$110.0886	$110.09	$110.10	$110.10
Purchase #2	$196.45	3.389%	$203.1077	$203.11	$203.10	$203.10
Purchase #3	$40.34	4.181%	$42.0266	$42.03	$42.05	$42.00
Purchase #4	$54.63	13.128%	$61.8018	$61.80	$61.80	$61.80
Purchase #5	$90.58	4.809%	$94.936	$94.94	$94.95	$94.90
Purchase #6	$55.72	11.866%	$62.3317	$62.33	$62.35	$62.30
Purchase #7	$76.38	9.705%	$83.7927	$83.79	$83.80	$83.80
7 purchase totals =	$614.50		$658.0851	$658.09	$658.15	$658.00