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	$88.48	8.255%	$95.784	$95.78	$95.80	$95.80
Purchase #2	$70.42	10.811%	$78.0331	$78.03	$78.05	$78.00
Purchase #3	$82.81	8.471%	$89.8248	$89.82	$89.80	$89.80
Purchase #4	$241.37	9.755%	$264.9156	$264.92	$264.90	$264.90
Purchase #5	$167.42	6.372%	$178.088	$178.09	$178.10	$178.10
Purchase #6	$182.56	3.535%	$189.0135	$189.01	$189.00	$189.00
Purchase #7	$93.47	3.867%	$97.0845	$97.08	$97.10	$97.10
7 purchase totals =	$926.53		$992.7435	$992.73	$992.75	$992.70