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	$179.58	7.220%	$192.5457	$192.55	$192.55	$192.50
Purchase #2	$120.60	4.782%	$126.3671	$126.37	$126.35	$126.40
Purchase #3	$34.76	9.168%	$37.9468	$37.95	$37.95	$37.90
Purchase #4	$139.79	5.744%	$147.8195	$147.82	$147.80	$147.80
Purchase #5	$136.52	10.387%	$150.7003	$150.70	$150.70	$150.70
Purchase #6	$223.40	11.526%	$249.1491	$249.15	$249.15	$249.10
Purchase #7	$200.80	9.234%	$219.3419	$219.34	$219.35	$219.30
7 purchase totals =	$1,035.45		$1,123.8704	$1,123.88	$1,123.85	$1,123.70