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	$180.36	5.661%	$190.5702	$190.57	$190.55	$190.60
Purchase #2	$81.87	5.383%	$86.2771	$86.28	$86.30	$86.30
Purchase #3	$76.39	4.515%	$79.839	$79.84	$79.85	$79.80
Purchase #4	$71.42	10.329%	$78.797	$78.80	$78.80	$78.80
Purchase #5	$233.80	10.659%	$258.7207	$258.72	$258.70	$258.70
Purchase #6	$246.80	7.717%	$265.8456	$265.85	$265.85	$265.80
Purchase #7	$95.77	10.131%	$105.4725	$105.47	$105.45	$105.50
7 purchase totals =	$986.41		$1,065.5221	$1,065.53	$1,065.50	$1,065.50