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	$165.43	6.346%	$175.9282	$175.93	$175.95	$175.90
Purchase #2	$94.60	9.331%	$103.4271	$103.43	$103.45	$103.40
Purchase #3	$26.77	3.508%	$27.7091	$27.71	$27.70	$27.70
Purchase #4	$43.39	3.782%	$45.031	$45.03	$45.05	$45.00
Purchase #5	$138.84	12.683%	$156.4491	$156.45	$156.45	$156.40
Purchase #6	$158.54	8.645%	$172.2458	$172.25	$172.25	$172.20
Purchase #7	$140.98	3.259%	$145.5745	$145.57	$145.55	$145.60
7 purchase totals =	$768.55		$826.3648	$826.37	$826.40	$826.20