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	$62.52	9.245%	$68.3	$68.30	$68.30	$68.30
Purchase #2	$63.86	12.850%	$72.066	$72.07	$72.05	$72.10
Purchase #3	$104.28	7.794%	$112.4076	$112.41	$112.40	$112.40
Purchase #4	$221.52	10.171%	$244.0508	$244.05	$244.05	$244.10
Purchase #5	$27.58	10.856%	$30.5741	$30.57	$30.55	$30.60
Purchase #6	$186.38	5.547%	$196.7185	$196.72	$196.70	$196.70
Purchase #7	$107.32	5.150%	$112.847	$112.85	$112.85	$112.80
7 purchase totals =	$773.46		$836.9640	$836.97	$836.90	$837.00