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	$180.27	6.204%	$191.454	$191.45	$191.45	$191.50
Purchase #2	$88.88	12.696%	$100.1642	$100.16	$100.15	$100.20
Purchase #3	$164.54	12.831%	$185.6521	$185.65	$185.65	$185.70
Purchase #4	$78.84	6.719%	$84.1373	$84.14	$84.15	$84.10
Purchase #5	$189.78	4.367%	$198.0677	$198.07	$198.05	$198.10
Purchase #6	$49.60	11.825%	$55.4652	$55.47	$55.45	$55.50
Purchase #7	$95.75	12.562%	$107.7781	$107.78	$107.80	$107.80
7 purchase totals =	$847.66		$922.7186	$922.72	$922.70	$922.90