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	$147.59	9.795%	$162.0464	$162.05	$162.05	$162.00
Purchase #2	$239.93	4.105%	$249.7791	$249.78	$249.80	$249.80
Purchase #3	$6.56	8.165%	$7.0956	$7.10	$7.10	$7.10
Purchase #4	$67.88	6.638%	$72.3859	$72.39	$72.40	$72.40
Purchase #5	$125.83	4.324%	$131.2709	$131.27	$131.25	$131.30
Purchase #6	$56.89	4.652%	$59.5365	$59.54	$59.55	$59.50
Purchase #7	$224.83	13.214%	$254.539	$254.54	$254.55	$254.50
7 purchase totals =	$869.51		$936.6534	$936.67	$936.70	$936.60