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	$132.42	5.749%	$140.0328	$140.03	$140.05	$140.00
Purchase #2	$26.53	5.257%	$27.9247	$27.92	$27.90	$27.90
Purchase #3	$25.46	7.346%	$27.3303	$27.33	$27.35	$27.30
Purchase #4	$129.77	11.667%	$144.9103	$144.91	$144.90	$144.90
Purchase #5	$42.27	8.683%	$45.9403	$45.94	$45.95	$45.90
Purchase #6	$48.29	11.758%	$53.9679	$53.97	$53.95	$54.00
Purchase #7	$69.53	5.328%	$73.2346	$73.23	$73.25	$73.20
7 purchase totals =	$474.27		$513.3409	$513.33	$513.35	$513.20