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	$78.73	8.558%	$85.4677	$85.47	$85.45	$85.50
Purchase #2	$151.68	10.777%	$168.0266	$168.03	$168.05	$168.00
Purchase #3	$212.77	12.630%	$239.6429	$239.64	$239.65	$239.60
Purchase #4	$64.52	12.356%	$72.4921	$72.49	$72.50	$72.50
Purchase #5	$190.72	3.524%	$197.441	$197.44	$197.45	$197.40
Purchase #6	$97.65	7.559%	$105.0314	$105.03	$105.05	$105.00
Purchase #7	$153.77	12.222%	$172.5638	$172.56	$172.55	$172.60
7 purchase totals =	$949.84		$1,040.6655	$1,040.66	$1,040.70	$1,040.60