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	$141.46	8.535%	$153.5336	$153.53	$153.55	$153.50
Purchase #2	$42.50	6.695%	$45.3454	$45.35	$45.35	$45.30
Purchase #3	$74.68	5.143%	$78.5208	$78.52	$78.50	$78.50
Purchase #4	$142.47	5.548%	$150.3742	$150.37	$150.35	$150.40
Purchase #5	$123.78	5.497%	$130.5842	$130.58	$130.60	$130.60
Purchase #6	$96.29	7.490%	$103.5021	$103.50	$103.50	$103.50
Purchase #7	$147.49	11.779%	$164.8628	$164.86	$164.85	$164.90
7 purchase totals =	$768.67		$826.7231	$826.71	$826.70	$826.70