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	$32.62	13.836%	$37.1333	$37.13	$37.15	$37.10
Purchase #2	$50.98	7.571%	$54.8397	$54.84	$54.85	$54.80
Purchase #3	$156.25	3.820%	$162.2188	$162.22	$162.20	$162.20
Purchase #4	$186.56	5.566%	$196.9439	$196.94	$196.95	$196.90
Purchase #5	$27.76	8.796%	$30.2018	$30.20	$30.20	$30.20
Purchase #6	$80.63	3.667%	$83.5867	$83.59	$83.60	$83.60
Purchase #7	$5.54	11.231%	$6.1622	$6.16	$6.15	$6.20
7 purchase totals =	$540.34		$571.0864	$571.08	$571.10	$571.00