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	$5.83	8.605%	$6.3317	$6.33	$6.35	$6.30
Purchase #2	$38.35	3.716%	$39.7751	$39.78	$39.80	$39.80
Purchase #3	$49.87	11.315%	$55.5128	$55.51	$55.50	$55.50
Purchase #4	$22.39	11.116%	$24.8789	$24.88	$24.90	$24.90
Purchase #5	$67.38	5.165%	$70.8602	$70.86	$70.85	$70.90
Purchase #6	$18.63	11.258%	$20.7274	$20.73	$20.75	$20.70
Purchase #7	$132.41	13.558%	$150.3621	$150.36	$150.35	$150.40
7 purchase totals =	$334.86		$368.4482	$368.45	$368.50	$368.50