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	$165.43	10.286%	$182.4461	$182.45	$182.45	$182.40
Purchase #2	$20.37	6.292%	$21.6517	$21.65	$21.65	$21.70
Purchase #3	$161.73	11.658%	$180.5845	$180.58	$180.60	$180.60
Purchase #4	$146.81	10.565%	$162.3205	$162.32	$162.30	$162.30
Purchase #5	$51.41	10.107%	$56.606	$56.61	$56.60	$56.60
Purchase #6	$196.71	6.228%	$208.9611	$208.96	$208.95	$209.00
Purchase #7	$179.77	13.758%	$204.5028	$204.50	$204.50	$204.50
7 purchase totals =	$922.23		$1,017.0727	$1,017.07	$1,017.05	$1,017.10