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	$86.27	4.123%	$89.8269	$89.83	$89.85	$89.80
Purchase #2	$52.72	3.419%	$54.5225	$54.52	$54.50	$54.50
Purchase #3	$73.83	3.312%	$76.2752	$76.28	$76.30	$76.30
Purchase #4	$212.90	11.682%	$237.771	$237.77	$237.75	$237.80
Purchase #5	$112.79	8.691%	$122.5926	$122.59	$122.60	$122.60
Purchase #6	$109.27	13.156%	$123.6456	$123.65	$123.65	$123.60
Purchase #7	$197.63	10.674%	$218.725	$218.73	$218.75	$218.70
7 purchase totals =	$845.41		$923.3588	$923.37	$923.40	$923.30