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	$59.49	10.600%	$65.7959	$65.80	$65.80	$65.80
Purchase #2	$127.49	11.496%	$142.1463	$142.15	$142.15	$142.10
Purchase #3	$26.63	8.447%	$28.8794	$28.88	$28.90	$28.90
Purchase #4	$84.39	8.778%	$91.7978	$91.80	$91.80	$91.80
Purchase #5	$215.95	9.507%	$236.4804	$236.48	$236.50	$236.50
Purchase #6	$145.83	7.558%	$156.8518	$156.85	$156.85	$156.90
Purchase #7	$145.52	10.352%	$160.5842	$160.58	$160.60	$160.60
7 purchase totals =	$805.30		$882.5358	$882.54	$882.60	$882.60