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	$140.49	9.108%	$153.2858	$153.29	$153.30	$153.30
Purchase #2	$183.66	8.421%	$199.126	$199.13	$199.15	$199.10
Purchase #3	$148.96	6.218%	$158.2223	$158.22	$158.20	$158.20
Purchase #4	$89.90	10.845%	$99.6497	$99.65	$99.65	$99.60
Purchase #5	$219.80	13.691%	$249.8928	$249.89	$249.90	$249.90
Purchase #6	$167.93	10.657%	$185.8263	$185.83	$185.85	$185.80
Purchase #7	$169.64	9.203%	$185.252	$185.25	$185.25	$185.30
7 purchase totals =	$1,120.38		$1,231.2549	$1,231.26	$1,231.30	$1,231.20