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	$176.28	5.191%	$185.4307	$185.43	$185.45	$185.40
Purchase #2	$168.50	8.185%	$182.2917	$182.29	$182.30	$182.30
Purchase #3	$73.97	13.431%	$83.9049	$83.90	$83.90	$83.90
Purchase #4	$128.35	7.358%	$137.794	$137.79	$137.80	$137.80
Purchase #5	$175.77	5.773%	$185.9172	$185.92	$185.90	$185.90
Purchase #6	$156.36	12.762%	$176.3147	$176.31	$176.30	$176.30
Purchase #7	$36.25	5.691%	$38.313	$38.31	$38.30	$38.30
7 purchase totals =	$915.48		$989.9662	$989.95	$989.95	$989.90