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	$64.63	12.228%	$72.533	$72.53	$72.55	$72.50
Purchase #2	$213.27	5.490%	$224.9785	$224.98	$225.00	$225.00
Purchase #3	$6.77	10.671%	$7.4924	$7.49	$7.50	$7.50
Purchase #4	$122.41	8.790%	$133.1698	$133.17	$133.15	$133.20
Purchase #5	$250.29	11.796%	$279.8142	$279.81	$279.80	$279.80
Purchase #6	$168.58	11.425%	$187.8403	$187.84	$187.85	$187.80
Purchase #7	$152.82	11.621%	$170.5792	$170.58	$170.60	$170.60
7 purchase totals =	$978.77		$1,076.4074	$1,076.40	$1,076.45	$1,076.40