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	$166.46	10.152%	$183.359	$183.36	$183.35	$183.40
Purchase #2	$140.51	9.319%	$153.6041	$153.60	$153.60	$153.60
Purchase #3	$162.89	13.509%	$184.8948	$184.89	$184.90	$184.90
Purchase #4	$159.74	12.659%	$179.9615	$179.96	$179.95	$180.00
Purchase #5	$192.74	13.512%	$218.783	$218.78	$218.80	$218.80
Purchase #6	$44.33	3.417%	$45.8448	$45.84	$45.85	$45.80
Purchase #7	$145.61	13.874%	$165.8119	$165.81	$165.80	$165.80
7 purchase totals =	$1,012.28		$1,132.2591	$1,132.24	$1,132.25	$1,132.30