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	$35.36	4.106%	$36.8119	$36.81	$36.80	$36.80
Purchase #2	$103.58	4.172%	$107.9014	$107.90	$107.90	$107.90
Purchase #3	$180.52	10.557%	$199.5775	$199.58	$199.60	$199.60
Purchase #4	$234.95	8.607%	$255.1721	$255.17	$255.15	$255.20
Purchase #5	$96.28	13.562%	$109.3375	$109.34	$109.35	$109.30
Purchase #6	$115.58	7.162%	$123.8578	$123.86	$123.85	$123.90
Purchase #7	$218.58	12.234%	$245.3211	$245.32	$245.30	$245.30
7 purchase totals =	$984.85		$1,077.9793	$1,077.98	$1,077.95	$1,078.00