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	$53.48	11.412%	$59.5831	$59.58	$59.60	$59.60
Purchase #2	$152.77	13.737%	$173.756	$173.76	$173.75	$173.80
Purchase #3	$144.25	8.853%	$157.0205	$157.02	$157.00	$157.00
Purchase #4	$221.56	4.166%	$230.7902	$230.79	$230.80	$230.80
Purchase #5	$170.60	3.690%	$176.8951	$176.90	$176.90	$176.90
Purchase #6	$144.38	4.165%	$150.3934	$150.39	$150.40	$150.40
Purchase #7	$193.45	3.721%	$200.6483	$200.65	$200.65	$200.60
7 purchase totals =	$1,080.49		$1,149.0866	$1,149.09	$1,149.10	$1,149.10