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	$229.51	5.188%	$241.417	$241.42	$241.40	$241.40
Purchase #2	$97.83	6.225%	$103.9199	$103.92	$103.90	$103.90
Purchase #3	$32.41	9.415%	$35.4614	$35.46	$35.45	$35.50
Purchase #4	$166.50	11.741%	$186.0488	$186.05	$186.05	$186.00
Purchase #5	$135.44	13.714%	$154.0142	$154.01	$154.00	$154.00
Purchase #6	$41.86	11.228%	$46.56	$46.56	$46.55	$46.60
Purchase #7	$158.39	3.663%	$164.1918	$164.19	$164.20	$164.20
7 purchase totals =	$861.94		$931.6131	$931.61	$931.55	$931.60