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	$150.64	11.185%	$167.4891	$167.49	$167.50	$167.50
Purchase #2	$56.50	5.165%	$59.4182	$59.42	$59.40	$59.40
Purchase #3	$135.62	3.224%	$139.9924	$139.99	$140.00	$140.00
Purchase #4	$66.96	8.139%	$72.4099	$72.41	$72.40	$72.40
Purchase #5	$54.67	13.547%	$62.0761	$62.08	$62.10	$62.10
Purchase #6	$141.64	7.294%	$151.9712	$151.97	$151.95	$152.00
Purchase #7	$60.66	11.350%	$67.5449	$67.54	$67.55	$67.50
7 purchase totals =	$666.69		$720.9018	$720.90	$720.90	$720.90