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	$164.29	4.447%	$171.596	$171.60	$171.60	$171.60
Purchase #2	$90.98	10.108%	$100.1763	$100.18	$100.20	$100.20
Purchase #3	$197.88	11.739%	$221.1091	$221.11	$221.10	$221.10
Purchase #4	$69.50	13.580%	$78.9381	$78.94	$78.95	$78.90
Purchase #5	$64.50	6.364%	$68.6048	$68.60	$68.60	$68.60
Purchase #6	$213.58	4.249%	$222.655	$222.66	$222.65	$222.70
Purchase #7	$77.57	6.126%	$82.3219	$82.32	$82.30	$82.30
7 purchase totals =	$878.30		$945.4012	$945.41	$945.40	$945.40