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	$72.89	4.632%	$76.2663	$76.27	$76.25	$76.30
Purchase #2	$88.65	7.438%	$95.2438	$95.24	$95.25	$95.20
Purchase #3	$39.98	6.629%	$42.6303	$42.63	$42.65	$42.60
Purchase #4	$40.41	5.460%	$42.6164	$42.62	$42.60	$42.60
Purchase #5	$204.52	5.470%	$215.7072	$215.71	$215.70	$215.70
Purchase #6	$43.72	8.332%	$47.3628	$47.36	$47.35	$47.40
Purchase #7	$156.95	3.742%	$162.8231	$162.82	$162.80	$162.80
7 purchase totals =	$647.12		$682.6499	$682.65	$682.60	$682.60