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	$87.72	12.228%	$98.4464	$98.45	$98.45	$98.40
Purchase #2	$194.83	4.690%	$203.9675	$203.97	$203.95	$204.00
Purchase #3	$152.30	6.660%	$162.4432	$162.44	$162.45	$162.40
Purchase #4	$122.30	7.846%	$131.8957	$131.90	$131.90	$131.90
Purchase #5	$104.63	11.472%	$116.6332	$116.63	$116.65	$116.60
Purchase #6	$79.84	8.439%	$86.5777	$86.58	$86.60	$86.60
Purchase #7	$249.55	4.710%	$261.3038	$261.30	$261.30	$261.30
7 purchase totals =	$991.17		$1,061.2675	$1,061.27	$1,061.30	$1,061.20