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	$89.93	9.828%	$98.7683	$98.77	$98.75	$98.80
Purchase #2	$162.53	11.392%	$181.0454	$181.05	$181.05	$181.00
Purchase #3	$100.93	3.223%	$104.183	$104.18	$104.20	$104.20
Purchase #4	$153.78	12.176%	$172.5043	$172.50	$172.50	$172.50
Purchase #5	$37.82	8.809%	$41.1516	$41.15	$41.15	$41.20
Purchase #6	$146.92	3.514%	$152.0828	$152.08	$152.10	$152.10
Purchase #7	$133.64	11.351%	$148.8095	$148.81	$148.80	$148.80
7 purchase totals =	$825.55		$898.5449	$898.54	$898.55	$898.60