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	$158.77	8.260%	$171.8844	$171.88	$171.90	$171.90
Purchase #2	$101.27	8.183%	$109.5569	$109.56	$109.55	$109.60
Purchase #3	$80.94	11.508%	$90.2546	$90.25	$90.25	$90.30
Purchase #4	$112.88	8.324%	$122.2761	$122.28	$122.30	$122.30
Purchase #5	$41.57	10.470%	$45.9224	$45.92	$45.90	$45.90
Purchase #6	$69.29	11.800%	$77.4662	$77.47	$77.45	$77.50
Purchase #7	$115.36	7.761%	$124.3131	$124.31	$124.30	$124.30
7 purchase totals =	$680.08		$741.6737	$741.67	$741.65	$741.80