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	$215.86	12.847%	$243.5915	$243.59	$243.60	$243.60
Purchase #2	$66.78	7.360%	$71.695	$71.70	$71.70	$71.70
Purchase #3	$86.65	3.478%	$89.6637	$89.66	$89.65	$89.70
Purchase #4	$100.56	10.642%	$111.2616	$111.26	$111.25	$111.30
Purchase #5	$45.63	3.306%	$47.1385	$47.14	$47.15	$47.10
Purchase #6	$231.41	4.138%	$240.9857	$240.99	$241.00	$241.00
Purchase #7	$136.52	5.344%	$143.8156	$143.82	$143.80	$143.80
7 purchase totals =	$883.41		$948.1516	$948.16	$948.15	$948.20