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	$212.59	5.581%	$224.4546	$224.45	$224.45	$224.50
Purchase #2	$75.41	8.110%	$81.5258	$81.53	$81.55	$81.50
Purchase #3	$53.54	3.327%	$55.3213	$55.32	$55.30	$55.30
Purchase #4	$106.39	12.719%	$119.9217	$119.92	$119.90	$119.90
Purchase #5	$165.67	3.812%	$171.9853	$171.99	$172.00	$172.00
Purchase #6	$171.82	7.815%	$185.2477	$185.25	$185.25	$185.20
Purchase #7	$160.88	4.111%	$167.4938	$167.49	$167.50	$167.50
7 purchase totals =	$946.30		$1,005.9502	$1,005.95	$1,005.95	$1,005.90