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	$41.85	6.233%	$44.4585	$44.46	$44.45	$44.50
Purchase #2	$60.83	11.597%	$67.8845	$67.88	$67.90	$67.90
Purchase #3	$25.90	5.754%	$27.3903	$27.39	$27.40	$27.40
Purchase #4	$156.83	7.728%	$168.9498	$168.95	$168.95	$168.90
Purchase #5	$121.83	3.470%	$126.0575	$126.06	$126.05	$126.10
Purchase #6	$32.63	8.373%	$35.3621	$35.36	$35.35	$35.40
Purchase #7	$203.86	11.518%	$227.3406	$227.34	$227.35	$227.30
7 purchase totals =	$643.73		$697.4433	$697.44	$697.45	$697.50