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	$103.93	9.764%	$114.0777	$114.08	$114.10	$114.10
Purchase #2	$70.85	9.770%	$77.772	$77.77	$77.75	$77.80
Purchase #3	$43.86	5.165%	$46.1254	$46.13	$46.15	$46.10
Purchase #4	$160.50	3.379%	$165.9233	$165.92	$165.90	$165.90
Purchase #5	$171.81	10.134%	$189.2212	$189.22	$189.20	$189.20
Purchase #6	$105.25	8.851%	$114.5657	$114.57	$114.55	$114.60
Purchase #7	$85.41	10.622%	$94.4823	$94.48	$94.50	$94.50
7 purchase totals =	$741.61		$802.1676	$802.17	$802.15	$802.20