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	$74.74	5.553%	$78.8903	$78.89	$78.90	$78.90
Purchase #2	$23.86	4.241%	$24.8719	$24.87	$24.85	$24.90
Purchase #3	$40.76	4.550%	$42.6146	$42.61	$42.60	$42.60
Purchase #4	$38.98	9.816%	$42.8063	$42.81	$42.80	$42.80
Purchase #5	$182.58	10.589%	$201.9134	$201.91	$201.90	$201.90
Purchase #6	$230.35	6.436%	$245.1753	$245.18	$245.20	$245.20
Purchase #7	$140.57	3.687%	$145.7528	$145.75	$145.75	$145.80
7 purchase totals =	$731.84		$782.0246	$782.02	$782.00	$782.10