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	$154.32	3.833%	$160.2351	$160.24	$160.25	$160.20
Purchase #2	$77.82	8.664%	$84.5623	$84.56	$84.55	$84.60
Purchase #3	$113.61	9.384%	$124.2712	$124.27	$124.25	$124.30
Purchase #4	$168.88	6.191%	$179.3354	$179.34	$179.35	$179.30
Purchase #5	$135.81	11.514%	$151.4472	$151.45	$151.45	$151.40
Purchase #6	$111.48	10.359%	$123.0282	$123.03	$123.05	$123.00
Purchase #7	$168.46	9.539%	$184.5294	$184.53	$184.55	$184.50
7 purchase totals =	$930.38		$1,007.4088	$1,007.42	$1,007.45	$1,007.30