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	$146.27	7.415%	$157.1159	$157.12	$157.10	$157.10
Purchase #2	$156.38	7.796%	$168.5714	$168.57	$168.55	$168.60
Purchase #3	$228.38	5.840%	$241.7174	$241.72	$241.70	$241.70
Purchase #4	$88.71	13.331%	$100.5359	$100.54	$100.55	$100.50
Purchase #5	$109.47	9.427%	$119.7897	$119.79	$119.80	$119.80
Purchase #6	$9.72	5.483%	$10.2529	$10.25	$10.25	$10.30
Purchase #7	$103.87	3.508%	$107.5138	$107.51	$107.50	$107.50
7 purchase totals =	$842.80		$905.4970	$905.50	$905.45	$905.50