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	$119.26	3.439%	$123.3614	$123.36	$123.35	$123.40
Purchase #2	$120.51	9.551%	$132.0199	$132.02	$132.00	$132.00
Purchase #3	$157.73	13.676%	$179.3012	$179.30	$179.30	$179.30
Purchase #4	$96.56	7.562%	$103.8619	$103.86	$103.85	$103.90
Purchase #5	$25.59	7.763%	$27.5766	$27.58	$27.60	$27.60
Purchase #6	$79.97	11.691%	$89.3193	$89.32	$89.30	$89.30
Purchase #7	$201.99	5.582%	$213.2651	$213.27	$213.25	$213.30
7 purchase totals =	$801.61		$868.7054	$868.71	$868.65	$868.80