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	$28.89	7.732%	$31.1238	$31.12	$31.10	$31.10
Purchase #2	$208.67	6.226%	$221.6618	$221.66	$221.65	$221.70
Purchase #3	$172.86	3.440%	$178.8064	$178.81	$178.80	$178.80
Purchase #4	$204.89	8.699%	$222.7134	$222.71	$222.70	$222.70
Purchase #5	$140.79	3.228%	$145.3347	$145.33	$145.35	$145.30
Purchase #6	$96.69	3.782%	$100.3468	$100.35	$100.35	$100.30
Purchase #7	$179.59	3.812%	$186.436	$186.44	$186.45	$186.40
7 purchase totals =	$1,032.38		$1,086.4229	$1,086.42	$1,086.40	$1,086.30