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	$194.75	5.685%	$205.8215	$205.82	$205.80	$205.80
Purchase #2	$145.63	11.555%	$162.4575	$162.46	$162.45	$162.50
Purchase #3	$179.51	13.531%	$203.7995	$203.80	$203.80	$203.80
Purchase #4	$208.81	4.599%	$218.4132	$218.41	$218.40	$218.40
Purchase #5	$40.98	8.190%	$44.3363	$44.34	$44.35	$44.30
Purchase #6	$57.57	6.452%	$61.2844	$61.28	$61.30	$61.30
Purchase #7	$40.48	12.247%	$45.4376	$45.44	$45.45	$45.40
7 purchase totals =	$867.73		$941.5500	$941.55	$941.55	$941.50