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	$152.73	12.526%	$171.861	$171.86	$171.85	$171.90
Purchase #2	$90.37	5.758%	$95.5735	$95.57	$95.55	$95.60
Purchase #3	$103.86	5.310%	$109.375	$109.38	$109.40	$109.40
Purchase #4	$172.72	6.256%	$183.5254	$183.53	$183.55	$183.50
Purchase #5	$177.90	8.538%	$193.0891	$193.09	$193.10	$193.10
Purchase #6	$216.95	5.577%	$229.0493	$229.05	$229.05	$229.00
Purchase #7	$104.73	12.731%	$118.0632	$118.06	$118.05	$118.10
7 purchase totals =	$1,019.26		$1,100.5365	$1,100.54	$1,100.55	$1,100.60