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	$41.69	10.626%	$46.12	$46.12	$46.10	$46.10
Purchase #2	$181.81	13.482%	$206.3216	$206.32	$206.30	$206.30
Purchase #3	$174.96	10.279%	$192.9441	$192.94	$192.95	$192.90
Purchase #4	$41.86	3.716%	$43.4155	$43.42	$43.40	$43.40
Purchase #5	$71.43	10.420%	$78.873	$78.87	$78.85	$78.90
Purchase #6	$51.37	5.363%	$54.125	$54.13	$54.15	$54.10
Purchase #7	$150.52	13.624%	$171.0268	$171.03	$171.05	$171.00
7 purchase totals =	$713.64		$792.8260	$792.83	$792.80	$792.70