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	$152.26	7.732%	$164.0327	$164.03	$164.05	$164.00
Purchase #2	$198.47	12.386%	$223.0525	$223.05	$223.05	$223.10
Purchase #3	$81.41	7.608%	$87.6037	$87.60	$87.60	$87.60
Purchase #4	$201.95	6.722%	$215.5251	$215.53	$215.55	$215.50
Purchase #5	$40.67	7.728%	$43.813	$43.81	$43.80	$43.80
Purchase #6	$142.91	5.234%	$150.3899	$150.39	$150.40	$150.40
Purchase #7	$87.56	3.785%	$90.8741	$90.87	$90.85	$90.90
7 purchase totals =	$905.23		$975.2910	$975.28	$975.30	$975.30