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	$51.73	6.505%	$55.095	$55.10	$55.10	$55.10
Purchase #2	$242.48	9.153%	$264.6742	$264.67	$264.65	$264.70
Purchase #3	$227.39	9.620%	$249.2649	$249.26	$249.25	$249.30
Purchase #4	$62.50	5.730%	$66.0813	$66.08	$66.10	$66.10
Purchase #5	$68.51	5.835%	$72.5076	$72.51	$72.50	$72.50
Purchase #6	$211.87	6.326%	$225.2729	$225.27	$225.25	$225.30
Purchase #7	$209.43	10.594%	$231.617	$231.62	$231.60	$231.60
7 purchase totals =	$1,073.91		$1,164.5129	$1,164.51	$1,164.45	$1,164.60