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	$211.75	7.492%	$227.6143	$227.61	$227.60	$227.60
Purchase #2	$101.88	10.459%	$112.5356	$112.54	$112.55	$112.50
Purchase #3	$26.28	5.162%	$27.6366	$27.64	$27.65	$27.60
Purchase #4	$16.39	6.791%	$17.503	$17.50	$17.50	$17.50
Purchase #5	$217.72	12.814%	$245.6186	$245.62	$245.60	$245.60
Purchase #6	$92.43	8.151%	$99.964	$99.96	$99.95	$100.00
Purchase #7	$159.36	12.151%	$178.7238	$178.72	$178.70	$178.70
7 purchase totals =	$825.81		$909.5959	$909.59	$909.55	$909.50