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	$82.79	3.357%	$85.5693	$85.57	$85.55	$85.60
Purchase #2	$151.37	13.515%	$171.8277	$171.83	$171.85	$171.80
Purchase #3	$15.28	5.822%	$16.1696	$16.17	$16.15	$16.20
Purchase #4	$78.95	8.337%	$85.5321	$85.53	$85.55	$85.50
Purchase #5	$84.76	12.722%	$95.5432	$95.54	$95.55	$95.50
Purchase #6	$91.83	12.786%	$103.5714	$103.57	$103.55	$103.60
Purchase #7	$89.33	12.663%	$100.6419	$100.64	$100.65	$100.60
7 purchase totals =	$594.31		$658.8552	$658.85	$658.85	$658.80