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	$150.67	3.605%	$156.1017	$156.10	$156.10	$156.10
Purchase #2	$70.33	13.276%	$79.667	$79.67	$79.65	$79.70
Purchase #3	$62.27	7.638%	$67.0262	$67.03	$67.05	$67.00
Purchase #4	$182.61	11.495%	$203.601	$203.60	$203.60	$203.60
Purchase #5	$96.80	7.830%	$104.3794	$104.38	$104.40	$104.40
Purchase #6	$134.98	7.796%	$145.503	$145.50	$145.50	$145.50
Purchase #7	$233.61	11.217%	$259.814	$259.81	$259.80	$259.80
7 purchase totals =	$931.27		$1,016.0923	$1,016.09	$1,016.10	$1,016.10