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	$30.91	8.661%	$33.5871	$33.59	$33.60	$33.60
Purchase #2	$152.69	6.364%	$162.4072	$162.41	$162.40	$162.40
Purchase #3	$196.62	10.810%	$217.8746	$217.87	$217.85	$217.90
Purchase #4	$43.87	10.110%	$48.3053	$48.31	$48.30	$48.30
Purchase #5	$211.71	12.829%	$238.8703	$238.87	$238.85	$238.90
Purchase #6	$136.77	11.834%	$152.9554	$152.96	$152.95	$153.00
Purchase #7	$250.95	5.477%	$264.6945	$264.69	$264.70	$264.70
7 purchase totals =	$1,023.52		$1,118.6944	$1,118.70	$1,118.65	$1,118.80