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	$126.75	4.862%	$132.9126	$132.91	$132.90	$132.90
Purchase #2	$56.29	12.222%	$63.1698	$63.17	$63.15	$63.20
Purchase #3	$139.86	6.281%	$148.6446	$148.64	$148.65	$148.60
Purchase #4	$219.68	8.443%	$238.2276	$238.23	$238.25	$238.20
Purchase #5	$31.77	3.437%	$32.8619	$32.86	$32.85	$32.90
Purchase #6	$38.50	12.411%	$43.2782	$43.28	$43.30	$43.30
Purchase #7	$91.51	7.373%	$98.257	$98.26	$98.25	$98.30
7 purchase totals =	$704.36		$757.3517	$757.35	$757.35	$757.40