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	$137.37	11.514%	$153.1868	$153.19	$153.20	$153.20
Purchase #2	$53.91	9.690%	$59.1339	$59.13	$59.15	$59.10
Purchase #3	$62.40	3.530%	$64.6027	$64.60	$64.60	$64.60
Purchase #4	$28.45	12.109%	$31.895	$31.90	$31.90	$31.90
Purchase #5	$133.97	12.428%	$150.6198	$150.62	$150.60	$150.60
Purchase #6	$132.83	5.701%	$140.4026	$140.40	$140.40	$140.40
Purchase #7	$240.33	11.222%	$267.2998	$267.30	$267.30	$267.30
7 purchase totals =	$789.26		$867.1406	$867.14	$867.15	$867.10