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	$90.55	8.240%	$98.0113	$98.01	$98.00	$98.00
Purchase #2	$72.54	5.572%	$76.5819	$76.58	$76.60	$76.60
Purchase #3	$103.85	7.833%	$111.9846	$111.98	$112.00	$112.00
Purchase #4	$68.30	4.407%	$71.31	$71.31	$71.30	$71.30
Purchase #5	$6.83	13.851%	$7.776	$7.78	$7.80	$7.80
Purchase #6	$95.42	8.502%	$103.5326	$103.53	$103.55	$103.50
Purchase #7	$24.56	7.736%	$26.46	$26.46	$26.45	$26.50
7 purchase totals =	$462.05		$495.6564	$495.65	$495.70	$495.70