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	$134.36	5.738%	$142.0696	$142.07	$142.05	$142.10
Purchase #2	$48.86	10.159%	$53.8237	$53.82	$53.80	$53.80
Purchase #3	$57.90	6.315%	$61.5564	$61.56	$61.55	$61.60
Purchase #4	$79.66	3.150%	$82.1693	$82.17	$82.15	$82.20
Purchase #5	$247.65	6.149%	$262.878	$262.88	$262.90	$262.90
Purchase #6	$63.42	4.447%	$66.2403	$66.24	$66.25	$66.20
Purchase #7	$168.88	12.738%	$190.3919	$190.39	$190.40	$190.40
7 purchase totals =	$800.73		$859.1292	$859.13	$859.10	$859.20