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	$23.47	8.470%	$25.4579	$25.46	$25.45	$25.50
Purchase #2	$119.83	12.672%	$135.0149	$135.01	$135.00	$135.00
Purchase #3	$236.74	8.479%	$256.8132	$256.81	$256.80	$256.80
Purchase #4	$82.78	3.718%	$85.8578	$85.86	$85.85	$85.90
Purchase #5	$179.26	3.383%	$185.3244	$185.32	$185.30	$185.30
Purchase #6	$9.76	10.734%	$10.8076	$10.81	$10.80	$10.80
Purchase #7	$61.61	8.692%	$66.9651	$66.97	$66.95	$67.00
7 purchase totals =	$713.45		$766.2409	$766.24	$766.15	$766.30