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	$79.48	8.687%	$86.3844	$86.38	$86.40	$86.40
Purchase #2	$88.66	13.478%	$100.6096	$100.61	$100.60	$100.60
Purchase #3	$244.88	8.392%	$265.4303	$265.43	$265.45	$265.40
Purchase #4	$69.27	6.411%	$73.7109	$73.71	$73.70	$73.70
Purchase #5	$83.66	8.593%	$90.8489	$90.85	$90.85	$90.80
Purchase #6	$6.57	13.231%	$7.4393	$7.44	$7.45	$7.40
Purchase #7	$223.38	3.439%	$231.062	$231.06	$231.05	$231.10
7 purchase totals =	$795.90		$855.4854	$855.48	$855.50	$855.40