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	$178.89	9.308%	$195.5411	$195.54	$195.55	$195.50
Purchase #2	$229.51	8.468%	$248.9449	$248.94	$248.95	$248.90
Purchase #3	$17.34	7.671%	$18.6702	$18.67	$18.65	$18.70
Purchase #4	$98.56	3.155%	$101.6696	$101.67	$101.65	$101.70
Purchase #5	$214.25	13.719%	$243.643	$243.64	$243.65	$243.60
Purchase #6	$75.35	3.535%	$78.0136	$78.01	$78.00	$78.00
Purchase #7	$35.42	5.633%	$37.4152	$37.42	$37.40	$37.40
7 purchase totals =	$849.32		$923.8976	$923.89	$923.85	$923.80