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	$179.74	3.197%	$185.4863	$185.49	$185.50	$185.50
Purchase #2	$166.60	3.745%	$172.8392	$172.84	$172.85	$172.80
Purchase #3	$37.61	13.776%	$42.7912	$42.79	$42.80	$42.80
Purchase #4	$154.82	8.299%	$167.6685	$167.67	$167.65	$167.70
Purchase #5	$246.92	7.233%	$264.7797	$264.78	$264.80	$264.80
Purchase #6	$250.29	9.182%	$273.2716	$273.27	$273.25	$273.30
Purchase #7	$146.34	9.837%	$160.7355	$160.74	$160.75	$160.70
7 purchase totals =	$1,182.32		$1,267.5720	$1,267.58	$1,267.60	$1,267.60