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	$145.38	5.299%	$153.0837	$153.08	$153.10	$153.10
Purchase #2	$162.77	3.261%	$168.0779	$168.08	$168.10	$168.10
Purchase #3	$191.77	11.335%	$213.5071	$213.51	$213.50	$213.50
Purchase #4	$85.85	5.243%	$90.3511	$90.35	$90.35	$90.40
Purchase #5	$196.29	10.474%	$216.8494	$216.85	$216.85	$216.80
Purchase #6	$20.29	3.705%	$21.0417	$21.04	$21.05	$21.00
Purchase #7	$202.54	13.275%	$229.4272	$229.43	$229.45	$229.40
7 purchase totals =	$1,004.89		$1,092.3381	$1,092.34	$1,092.40	$1,092.30