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	$116.29	9.259%	$127.0573	$127.06	$127.05	$127.10
Purchase #2	$89.89	8.870%	$97.8632	$97.86	$97.85	$97.90
Purchase #3	$22.43	12.561%	$25.2474	$25.25	$25.25	$25.20
Purchase #4	$47.30	9.235%	$51.6682	$51.67	$51.65	$51.70
Purchase #5	$78.58	13.298%	$89.0296	$89.03	$89.05	$89.00
Purchase #6	$113.34	8.755%	$123.2629	$123.26	$123.25	$123.30
Purchase #7	$56.65	13.530%	$64.3147	$64.31	$64.30	$64.30
7 purchase totals =	$524.48		$578.4433	$578.44	$578.40	$578.50