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	$59.97	12.141%	$67.251	$67.25	$67.25	$67.30
Purchase #2	$75.88	8.500%	$82.3298	$82.33	$82.35	$82.30
Purchase #3	$157.81	8.505%	$171.2317	$171.23	$171.25	$171.20
Purchase #4	$6.94	9.817%	$7.6213	$7.62	$7.60	$7.60
Purchase #5	$166.77	11.411%	$185.8001	$185.80	$185.80	$185.80
Purchase #6	$24.50	10.259%	$27.0135	$27.01	$27.00	$27.00
Purchase #7	$82.55	5.555%	$87.1357	$87.14	$87.15	$87.10
7 purchase totals =	$574.42		$628.3831	$628.38	$628.40	$628.30