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	$90.46	4.872%	$94.8672	$94.87	$94.85	$94.90
Purchase #2	$85.98	10.789%	$95.2564	$95.26	$95.25	$95.30
Purchase #3	$7.47	4.353%	$7.7952	$7.80	$7.80	$7.80
Purchase #4	$205.84	10.371%	$227.1877	$227.19	$227.20	$227.20
Purchase #5	$100.38	7.840%	$108.2498	$108.25	$108.25	$108.20
Purchase #6	$215.96	11.171%	$240.0849	$240.08	$240.10	$240.10
Purchase #7	$151.52	11.163%	$168.4342	$168.43	$168.45	$168.40
7 purchase totals =	$857.61		$941.8754	$941.88	$941.90	$941.90