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	$215.32	6.789%	$229.9381	$229.94	$229.95	$229.90
Purchase #2	$139.81	8.174%	$151.2381	$151.24	$151.25	$151.20
Purchase #3	$50.54	11.110%	$56.155	$56.16	$56.15	$56.20
Purchase #4	$102.37	3.303%	$105.7513	$105.75	$105.75	$105.80
Purchase #5	$212.91	8.624%	$231.2714	$231.27	$231.25	$231.30
Purchase #6	$146.46	12.349%	$164.5463	$164.55	$164.55	$164.50
Purchase #7	$164.48	3.820%	$170.7631	$170.76	$170.75	$170.80
7 purchase totals =	$1,031.89		$1,109.6633	$1,109.67	$1,109.65	$1,109.70