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	$69.30	4.231%	$72.2321	$72.23	$72.25	$72.20
Purchase #2	$136.39	4.858%	$143.0158	$143.02	$143.00	$143.00
Purchase #3	$130.91	10.493%	$144.6464	$144.65	$144.65	$144.60
Purchase #4	$49.55	11.160%	$55.0798	$55.08	$55.10	$55.10
Purchase #5	$87.59	4.627%	$91.6428	$91.64	$91.65	$91.60
Purchase #6	$249.71	11.869%	$279.3481	$279.35	$279.35	$279.30
Purchase #7	$219.41	6.120%	$232.8379	$232.84	$232.85	$232.80
7 purchase totals =	$942.86		$1,018.8029	$1,018.81	$1,018.85	$1,018.60