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	$61.69	5.516%	$65.0928	$65.09	$65.10	$65.10
Purchase #2	$184.44	7.806%	$198.8374	$198.84	$198.85	$198.80
Purchase #3	$40.27	6.315%	$42.8131	$42.81	$42.80	$42.80
Purchase #4	$103.34	5.437%	$108.9586	$108.96	$108.95	$109.00
Purchase #5	$94.96	5.710%	$100.3822	$100.38	$100.40	$100.40
Purchase #6	$203.82	12.799%	$229.9069	$229.91	$229.90	$229.90
Purchase #7	$25.48	7.661%	$27.432	$27.43	$27.45	$27.40
7 purchase totals =	$714.00		$773.4230	$773.42	$773.45	$773.40