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	$154.65	11.687%	$172.7239	$172.72	$172.70	$172.70
Purchase #2	$106.57	10.298%	$117.5446	$117.54	$117.55	$117.50
Purchase #3	$98.47	9.746%	$108.0669	$108.07	$108.05	$108.10
Purchase #4	$187.29	4.667%	$196.0308	$196.03	$196.05	$196.00
Purchase #5	$34.90	4.850%	$36.5927	$36.59	$36.60	$36.60
Purchase #6	$11.64	5.861%	$12.3222	$12.32	$12.30	$12.30
Purchase #7	$154.41	11.165%	$171.6499	$171.65	$171.65	$171.60
7 purchase totals =	$747.93		$814.9310	$814.92	$814.90	$814.80