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	$173.80	8.555%	$188.6686	$188.67	$188.65	$188.70
Purchase #2	$236.89	10.506%	$261.7777	$261.78	$261.80	$261.80
Purchase #3	$24.53	5.610%	$25.9061	$25.91	$25.90	$25.90
Purchase #4	$224.34	11.497%	$250.1324	$250.13	$250.15	$250.10
Purchase #5	$63.78	4.377%	$66.5717	$66.57	$66.55	$66.60
Purchase #6	$155.86	5.787%	$164.8796	$164.88	$164.90	$164.90
Purchase #7	$81.95	9.829%	$90.0049	$90.00	$90.00	$90.00
7 purchase totals =	$961.15		$1,047.9410	$1,047.94	$1,047.95	$1,048.00