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	$143.57	6.155%	$152.4067	$152.41	$152.40	$152.40
Purchase #2	$167.33	13.834%	$190.4784	$190.48	$190.50	$190.50
Purchase #3	$174.27	6.634%	$185.8311	$185.83	$185.85	$185.80
Purchase #4	$34.44	11.804%	$38.5053	$38.51	$38.50	$38.50
Purchase #5	$158.78	5.193%	$167.0254	$167.03	$167.05	$167.00
Purchase #6	$169.36	10.508%	$187.1563	$187.16	$187.15	$187.20
Purchase #7	$164.86	8.710%	$179.2193	$179.22	$179.20	$179.20
7 purchase totals =	$1,012.61		$1,100.6225	$1,100.64	$1,100.65	$1,100.60