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	$150.47	4.853%	$157.7723	$157.77	$157.75	$157.80
Purchase #2	$101.59	10.413%	$112.1686	$112.17	$112.15	$112.20
Purchase #3	$188.78	3.749%	$195.8574	$195.86	$195.85	$195.90
Purchase #4	$109.35	10.212%	$120.5168	$120.52	$120.50	$120.50
Purchase #5	$65.33	11.423%	$72.7926	$72.79	$72.80	$72.80
Purchase #6	$56.98	7.720%	$61.3789	$61.38	$61.40	$61.40
Purchase #7	$130.74	8.141%	$141.3835	$141.38	$141.40	$141.40
7 purchase totals =	$803.24		$861.8701	$861.87	$861.85	$862.00