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	$105.81	7.181%	$113.4082	$113.41	$113.40	$113.40
Purchase #2	$82.95	9.255%	$90.627	$90.63	$90.65	$90.60
Purchase #3	$13.52	7.219%	$14.496	$14.50	$14.50	$14.50
Purchase #4	$68.61	6.238%	$72.8899	$72.89	$72.90	$72.90
Purchase #5	$148.61	9.264%	$162.3772	$162.38	$162.40	$162.40
Purchase #6	$16.71	7.558%	$17.9729	$17.97	$17.95	$18.00
Purchase #7	$11.83	12.282%	$13.283	$13.28	$13.30	$13.30
7 purchase totals =	$448.04		$485.0542	$485.06	$485.10	$485.10