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	$127.62	11.180%	$141.8879	$141.89	$141.90	$141.90
Purchase #2	$116.27	10.242%	$128.1784	$128.18	$128.20	$128.20
Purchase #3	$33.30	11.133%	$37.0073	$37.01	$37.00	$37.00
Purchase #4	$56.91	9.680%	$62.4189	$62.42	$62.40	$62.40
Purchase #5	$47.52	8.638%	$51.6248	$51.62	$51.60	$51.60
Purchase #6	$51.80	12.429%	$58.2382	$58.24	$58.25	$58.20
Purchase #7	$186.82	12.310%	$209.8175	$209.82	$209.80	$209.80
7 purchase totals =	$620.24		$689.1730	$689.18	$689.15	$689.10