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	$175.61	5.814%	$185.82	$185.82	$185.80	$185.80
Purchase #2	$147.82	13.619%	$167.9516	$167.95	$167.95	$168.00
Purchase #3	$238.71	3.710%	$247.5661	$247.57	$247.55	$247.60
Purchase #4	$113.60	4.128%	$118.2894	$118.29	$118.30	$118.30
Purchase #5	$104.91	11.184%	$116.6431	$116.64	$116.65	$116.60
Purchase #6	$67.90	6.222%	$72.1247	$72.12	$72.10	$72.10
Purchase #7	$73.41	4.428%	$76.6606	$76.66	$76.65	$76.70
7 purchase totals =	$921.96		$985.0555	$985.05	$985.00	$985.10