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	$104.41	9.495%	$114.3237	$114.32	$114.30	$114.30
Purchase #2	$38.50	9.845%	$42.2903	$42.29	$42.30	$42.30
Purchase #3	$164.82	13.828%	$187.6113	$187.61	$187.60	$187.60
Purchase #4	$55.92	9.738%	$61.3655	$61.37	$61.35	$61.40
Purchase #5	$40.42	13.681%	$45.9499	$45.95	$45.95	$45.90
Purchase #6	$206.49	7.267%	$221.4956	$221.50	$221.50	$221.50
Purchase #7	$91.87	6.781%	$98.0997	$98.10	$98.10	$98.10
7 purchase totals =	$702.43		$771.1360	$771.14	$771.10	$771.10