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	$105.61	10.597%	$116.8015	$116.80	$116.80	$116.80
Purchase #2	$218.27	5.377%	$230.0064	$230.01	$230.00	$230.00
Purchase #3	$59.38	10.155%	$65.41	$65.41	$65.40	$65.40
Purchase #4	$70.55	10.419%	$77.9006	$77.90	$77.90	$77.90
Purchase #5	$67.49	3.143%	$69.6112	$69.61	$69.60	$69.60
Purchase #6	$19.29	6.743%	$20.5907	$20.59	$20.60	$20.60
Purchase #7	$121.78	4.751%	$127.5658	$127.57	$127.55	$127.60
7 purchase totals =	$662.37		$707.8862	$707.89	$707.85	$707.90