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	$182.88	3.252%	$188.8273	$188.83	$188.85	$188.80
Purchase #2	$10.95	12.856%	$12.3577	$12.36	$12.35	$12.40
Purchase #3	$55.97	4.556%	$58.52	$58.52	$58.50	$58.50
Purchase #4	$53.41	5.507%	$56.3513	$56.35	$56.35	$56.40
Purchase #5	$192.88	13.821%	$219.5379	$219.54	$219.55	$219.50
Purchase #6	$32.88	7.212%	$35.2513	$35.25	$35.25	$35.30
Purchase #7	$215.62	6.461%	$229.5512	$229.55	$229.55	$229.60
7 purchase totals =	$744.59		$800.3967	$800.40	$800.40	$800.50