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	$85.98	4.525%	$89.8706	$89.87	$89.85	$89.90
Purchase #2	$90.80	7.794%	$97.877	$97.88	$97.90	$97.90
Purchase #3	$115.36	4.545%	$120.6031	$120.60	$120.60	$120.60
Purchase #4	$59.68	13.236%	$67.5792	$67.58	$67.60	$67.60
Purchase #5	$86.65	4.589%	$90.6264	$90.63	$90.65	$90.60
Purchase #6	$72.45	9.780%	$79.5356	$79.54	$79.55	$79.50
Purchase #7	$15.39	12.771%	$17.3555	$17.36	$17.35	$17.40
7 purchase totals =	$526.31		$563.4474	$563.46	$563.50	$563.50