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	$98.59	6.194%	$104.6967	$104.70	$104.70	$104.70
Purchase #2	$137.29	10.490%	$151.6917	$151.69	$151.70	$151.70
Purchase #3	$236.78	5.389%	$249.5401	$249.54	$249.55	$249.50
Purchase #4	$109.42	13.102%	$123.7562	$123.76	$123.75	$123.80
Purchase #5	$240.28	12.274%	$269.772	$269.77	$269.75	$269.80
Purchase #6	$31.27	8.261%	$33.8532	$33.85	$33.85	$33.90
Purchase #7	$75.69	9.397%	$82.8026	$82.80	$82.80	$82.80
7 purchase totals =	$929.32		$1,016.1125	$1,016.11	$1,016.10	$1,016.20