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	$22.75	6.401%	$24.2062	$24.21	$24.20	$24.20
Purchase #2	$144.31	5.601%	$152.3928	$152.39	$152.40	$152.40
Purchase #3	$144.67	4.363%	$150.982	$150.98	$151.00	$151.00
Purchase #4	$54.76	8.161%	$59.229	$59.23	$59.25	$59.20
Purchase #5	$83.35	4.208%	$86.8574	$86.86	$86.85	$86.90
Purchase #6	$196.91	10.302%	$217.1957	$217.20	$217.20	$217.20
Purchase #7	$76.71	11.654%	$85.6498	$85.65	$85.65	$85.60
7 purchase totals =	$723.46		$776.5129	$776.52	$776.55	$776.50