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	$114.79	4.733%	$120.223	$120.22	$120.20	$120.20
Purchase #2	$91.46	13.337%	$103.658	$103.66	$103.65	$103.70
Purchase #3	$26.47	4.617%	$27.6921	$27.69	$27.70	$27.70
Purchase #4	$96.89	12.692%	$109.1873	$109.19	$109.20	$109.20
Purchase #5	$142.83	5.564%	$150.7771	$150.78	$150.80	$150.80
Purchase #6	$112.92	12.258%	$126.7617	$126.76	$126.75	$126.80
Purchase #7	$139.61	5.732%	$147.6124	$147.61	$147.60	$147.60
7 purchase totals =	$724.97		$785.9116	$785.91	$785.90	$786.00