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	$216.44	5.569%	$228.4935	$228.49	$228.50	$228.50
Purchase #2	$114.58	12.855%	$129.3093	$129.31	$129.30	$129.30
Purchase #3	$242.70	9.851%	$266.6084	$266.61	$266.60	$266.60
Purchase #4	$90.39	12.657%	$101.8307	$101.83	$101.85	$101.80
Purchase #5	$187.73	6.764%	$200.4281	$200.43	$200.45	$200.40
Purchase #6	$73.78	12.406%	$82.9331	$82.93	$82.95	$82.90
Purchase #7	$145.48	4.808%	$152.4747	$152.47	$152.45	$152.50
7 purchase totals =	$1,071.10		$1,162.0778	$1,162.07	$1,162.10	$1,162.00