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	$222.38	5.234%	$234.0194	$234.02	$234.00	$234.00
Purchase #2	$136.72	7.530%	$147.015	$147.02	$147.00	$147.00
Purchase #3	$52.87	13.220%	$59.8594	$59.86	$59.85	$59.90
Purchase #4	$29.47	10.409%	$32.5375	$32.54	$32.55	$32.50
Purchase #5	$67.97	4.597%	$71.0946	$71.09	$71.10	$71.10
Purchase #6	$145.66	4.238%	$151.8331	$151.83	$151.85	$151.80
Purchase #7	$84.35	6.538%	$89.8648	$89.86	$89.85	$89.90
7 purchase totals =	$739.42		$786.2238	$786.22	$786.20	$786.20