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	$176.64	8.231%	$191.1792	$191.18	$191.20	$191.20
Purchase #2	$249.42	12.493%	$280.58	$280.58	$280.60	$280.60
Purchase #3	$37.43	11.219%	$41.6293	$41.63	$41.65	$41.60
Purchase #4	$100.95	8.540%	$109.5711	$109.57	$109.55	$109.60
Purchase #5	$39.69	6.422%	$42.2389	$42.24	$42.25	$42.20
Purchase #6	$54.97	8.492%	$59.6381	$59.64	$59.65	$59.60
Purchase #7	$234.91	7.675%	$252.9393	$252.94	$252.95	$252.90
7 purchase totals =	$894.01		$977.7759	$977.78	$977.85	$977.70