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	$76.59	11.651%	$85.5135	$85.51	$85.50	$85.50
Purchase #2	$117.88	12.456%	$132.5631	$132.56	$132.55	$132.60
Purchase #3	$184.41	7.668%	$198.5506	$198.55	$198.55	$198.60
Purchase #4	$250.72	12.785%	$282.7746	$282.77	$282.75	$282.80
Purchase #5	$101.35	13.638%	$115.1721	$115.17	$115.15	$115.20
Purchase #6	$61.86	6.380%	$65.8067	$65.81	$65.80	$65.80
Purchase #7	$185.73	7.458%	$199.5817	$199.58	$199.60	$199.60
7 purchase totals =	$978.54		$1,079.9623	$1,079.95	$1,079.90	$1,080.10