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	$247.97	7.830%	$267.3861	$267.39	$267.40	$267.40
Purchase #2	$190.95	11.240%	$212.4128	$212.41	$212.40	$212.40
Purchase #3	$37.96	9.409%	$41.5317	$41.53	$41.55	$41.50
Purchase #4	$40.33	3.186%	$41.6149	$41.61	$41.60	$41.60
Purchase #5	$89.72	12.597%	$101.022	$101.02	$101.00	$101.00
Purchase #6	$72.86	5.547%	$76.9015	$76.90	$76.90	$76.90
Purchase #7	$66.50	8.689%	$72.2782	$72.28	$72.30	$72.30
7 purchase totals =	$746.29		$813.1472	$813.14	$813.15	$813.10