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	$13.92	3.235%	$14.3703	$14.37	$14.35	$14.40
Purchase #2	$150.34	3.690%	$155.8875	$155.89	$155.90	$155.90
Purchase #3	$141.78	12.263%	$159.1665	$159.17	$159.15	$159.20
Purchase #4	$235.82	6.585%	$251.3487	$251.35	$251.35	$251.30
Purchase #5	$118.44	11.185%	$131.6875	$131.69	$131.70	$131.70
Purchase #6	$242.52	3.658%	$251.3914	$251.39	$251.40	$251.40
Purchase #7	$35.26	13.597%	$40.0543	$40.05	$40.05	$40.10
7 purchase totals =	$938.08		$1,003.9062	$1,003.91	$1,003.90	$1,004.00