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	$212.89	7.531%	$228.9227	$228.92	$228.90	$228.90
Purchase #2	$95.56	12.434%	$107.4419	$107.44	$107.45	$107.40
Purchase #3	$165.63	13.261%	$187.5942	$187.59	$187.60	$187.60
Purchase #4	$20.57	3.651%	$21.321	$21.32	$21.30	$21.30
Purchase #5	$56.82	3.835%	$58.999	$59.00	$59.00	$59.00
Purchase #6	$110.29	12.109%	$123.645	$123.65	$123.65	$123.60
Purchase #7	$94.79	5.105%	$99.629	$99.63	$99.65	$99.60
7 purchase totals =	$756.55		$827.5528	$827.55	$827.55	$827.40