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	$161.83	11.382%	$180.2495	$180.25	$180.25	$180.20
Purchase #2	$43.89	4.430%	$45.8343	$45.83	$45.85	$45.80
Purchase #3	$70.33	8.839%	$76.5465	$76.55	$76.55	$76.50
Purchase #4	$157.65	7.281%	$169.1285	$169.13	$169.15	$169.10
Purchase #5	$89.41	8.521%	$97.0286	$97.03	$97.05	$97.00
Purchase #6	$128.47	9.822%	$141.0883	$141.09	$141.10	$141.10
Purchase #7	$250.79	5.450%	$264.4581	$264.46	$264.45	$264.50
7 purchase totals =	$902.37		$974.3338	$974.34	$974.40	$974.20