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	$19.38	4.273%	$20.2081	$20.21	$20.20	$20.20
Purchase #2	$164.99	10.607%	$182.4905	$182.49	$182.50	$182.50
Purchase #3	$38.72	12.501%	$43.5604	$43.56	$43.55	$43.60
Purchase #4	$45.97	6.303%	$48.8675	$48.87	$48.85	$48.90
Purchase #5	$79.37	4.134%	$82.6512	$82.65	$82.65	$82.70
Purchase #6	$34.25	5.563%	$36.1553	$36.16	$36.15	$36.20
Purchase #7	$143.48	5.377%	$151.1949	$151.19	$151.20	$151.20
7 purchase totals =	$526.16		$565.1279	$565.13	$565.10	$565.30