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	$10.44	11.362%	$11.6262	$11.63	$11.65	$11.60
Purchase #2	$5.48	11.778%	$6.1254	$6.13	$6.15	$6.10
Purchase #3	$210.28	6.769%	$224.5139	$224.51	$224.50	$224.50
Purchase #4	$108.44	4.551%	$113.3751	$113.38	$113.40	$113.40
Purchase #5	$123.88	6.276%	$131.6547	$131.65	$131.65	$131.70
Purchase #6	$48.92	13.635%	$55.5902	$55.59	$55.60	$55.60
Purchase #7	$188.39	4.306%	$196.5021	$196.50	$196.50	$196.50
7 purchase totals =	$695.83		$739.3876	$739.39	$739.45	$739.40