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	$160.35	4.329%	$167.2916	$167.29	$167.30	$167.30
Purchase #2	$110.38	11.495%	$123.0682	$123.07	$123.05	$123.10
Purchase #3	$247.69	5.727%	$261.8752	$261.88	$261.90	$261.90
Purchase #4	$85.70	12.290%	$96.2325	$96.23	$96.25	$96.20
Purchase #5	$47.54	11.365%	$52.9429	$52.94	$52.95	$52.90
Purchase #6	$89.28	3.449%	$92.3593	$92.36	$92.35	$92.40
Purchase #7	$56.46	13.766%	$64.2323	$64.23	$64.25	$64.20
7 purchase totals =	$797.40		$858.0020	$858.00	$858.05	$858.00