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	$205.55	8.326%	$222.6641	$222.66	$222.65	$222.70
Purchase #2	$142.32	12.757%	$160.4758	$160.48	$160.50	$160.50
Purchase #3	$80.92	3.437%	$83.7012	$83.70	$83.70	$83.70
Purchase #4	$151.37	10.704%	$167.5726	$167.57	$167.55	$167.60
Purchase #5	$87.73	12.330%	$98.5471	$98.55	$98.55	$98.50
Purchase #6	$109.39	7.416%	$117.5024	$117.50	$117.50	$117.50
Purchase #7	$180.31	11.190%	$200.4867	$200.49	$200.50	$200.50
7 purchase totals =	$957.59		$1,050.9499	$1,050.95	$1,050.95	$1,051.00