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	$72.69	7.248%	$77.9586	$77.96	$77.95	$78.00
Purchase #2	$98.32	6.460%	$104.6715	$104.67	$104.65	$104.70
Purchase #3	$48.74	4.347%	$50.8587	$50.86	$50.85	$50.90
Purchase #4	$126.38	4.462%	$132.0191	$132.02	$132.00	$132.00
Purchase #5	$78.81	13.655%	$89.5715	$89.57	$89.55	$89.60
Purchase #6	$112.83	11.743%	$126.0796	$126.08	$126.10	$126.10
Purchase #7	$155.87	11.868%	$174.3687	$174.37	$174.35	$174.40
7 purchase totals =	$693.64		$755.5277	$755.53	$755.45	$755.70