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	$197.62	4.633%	$206.7757	$206.78	$206.80	$206.80
Purchase #2	$199.59	13.771%	$227.0755	$227.08	$227.10	$227.10
Purchase #3	$53.61	4.302%	$55.9163	$55.92	$55.90	$55.90
Purchase #4	$249.34	3.503%	$258.0744	$258.07	$258.05	$258.10
Purchase #5	$136.30	12.663%	$153.5597	$153.56	$153.55	$153.60
Purchase #6	$66.86	8.254%	$72.3786	$72.38	$72.40	$72.40
Purchase #7	$155.43	6.353%	$165.3045	$165.30	$165.30	$165.30
7 purchase totals =	$1,058.75		$1,139.0847	$1,139.09	$1,139.10	$1,139.20