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	$174.67	12.690%	$196.8356	$196.84	$196.85	$196.80
Purchase #2	$138.38	11.731%	$154.6134	$154.61	$154.60	$154.60
Purchase #3	$156.87	7.718%	$168.9772	$168.98	$169.00	$169.00
Purchase #4	$162.30	7.169%	$173.9353	$173.94	$173.95	$173.90
Purchase #5	$154.91	11.314%	$172.4365	$172.44	$172.45	$172.40
Purchase #6	$78.46	9.818%	$86.1632	$86.16	$86.15	$86.20
Purchase #7	$208.90	9.355%	$228.4426	$228.44	$228.45	$228.40
7 purchase totals =	$1,074.49		$1,181.4038	$1,181.41	$1,181.45	$1,181.30