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	$72.64	13.218%	$82.2416	$82.24	$82.25	$82.20
Purchase #2	$28.98	3.368%	$29.956	$29.96	$29.95	$30.00
Purchase #3	$61.57	3.192%	$63.5353	$63.54	$63.55	$63.50
Purchase #4	$104.79	6.294%	$111.3855	$111.39	$111.40	$111.40
Purchase #5	$102.43	8.703%	$111.3445	$111.34	$111.35	$111.30
Purchase #6	$36.86	11.589%	$41.1317	$41.13	$41.15	$41.10
Purchase #7	$43.84	3.733%	$45.4765	$45.48	$45.50	$45.50
7 purchase totals =	$451.11		$485.0711	$485.08	$485.15	$485.00