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	$12.80	8.481%	$13.8856	$13.89	$13.90	$13.90
Purchase #2	$78.79	6.464%	$83.883	$83.88	$83.90	$83.90
Purchase #3	$195.70	11.749%	$218.6928	$218.69	$218.70	$218.70
Purchase #4	$49.88	7.211%	$53.4768	$53.48	$53.50	$53.50
Purchase #5	$137.93	5.494%	$145.5079	$145.51	$145.50	$145.50
Purchase #6	$94.55	9.801%	$103.8168	$103.82	$103.80	$103.80
Purchase #7	$58.86	7.658%	$63.3675	$63.37	$63.35	$63.40
7 purchase totals =	$628.51		$682.6304	$682.64	$682.65	$682.70