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	$233.29	9.140%	$254.6127	$254.61	$254.60	$254.60
Purchase #2	$185.31	12.663%	$208.7758	$208.78	$208.80	$208.80
Purchase #3	$27.78	7.507%	$29.8654	$29.87	$29.85	$29.90
Purchase #4	$209.32	5.752%	$221.3601	$221.36	$221.35	$221.40
Purchase #5	$163.32	11.767%	$182.5379	$182.54	$182.55	$182.50
Purchase #6	$10.88	5.705%	$11.5007	$11.50	$11.50	$11.50
Purchase #7	$185.87	8.859%	$202.3362	$202.34	$202.35	$202.30
7 purchase totals =	$1,015.77		$1,110.9888	$1,111.00	$1,111.00	$1,111.00