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	$216.29	13.112%	$244.6499	$244.65	$244.65	$244.60
Purchase #2	$42.63	7.619%	$45.878	$45.88	$45.90	$45.90
Purchase #3	$24.92	12.260%	$27.9752	$27.98	$28.00	$28.00
Purchase #4	$158.77	7.737%	$171.054	$171.05	$171.05	$171.10
Purchase #5	$153.71	9.711%	$168.6368	$168.64	$168.65	$168.60
Purchase #6	$45.83	12.572%	$51.5917	$51.59	$51.60	$51.60
Purchase #7	$219.81	13.728%	$249.9855	$249.99	$250.00	$250.00
7 purchase totals =	$861.96		$959.7711	$959.78	$959.85	$959.80