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	$144.85	4.141%	$150.8482	$150.85	$150.85	$150.80
Purchase #2	$205.43	3.756%	$213.146	$213.15	$213.15	$213.10
Purchase #3	$82.32	6.253%	$87.4675	$87.47	$87.45	$87.50
Purchase #4	$168.51	13.161%	$190.6876	$190.69	$190.70	$190.70
Purchase #5	$81.56	12.758%	$91.9654	$91.97	$91.95	$92.00
Purchase #6	$67.89	10.701%	$75.1549	$75.15	$75.15	$75.20
Purchase #7	$177.88	10.249%	$196.1109	$196.11	$196.10	$196.10
7 purchase totals =	$928.44		$1,005.3805	$1,005.39	$1,005.35	$1,005.40