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	$32.34	5.738%	$34.1957	$34.20	$34.20	$34.20
Purchase #2	$114.80	11.431%	$127.9228	$127.92	$127.90	$127.90
Purchase #3	$202.50	6.378%	$215.4155	$215.42	$215.40	$215.40
Purchase #4	$135.53	9.851%	$148.8811	$148.88	$148.90	$148.90
Purchase #5	$65.48	10.164%	$72.1354	$72.14	$72.15	$72.10
Purchase #6	$149.93	13.343%	$169.9352	$169.94	$169.95	$169.90
Purchase #7	$158.35	5.560%	$167.1543	$167.15	$167.15	$167.20
7 purchase totals =	$858.93		$935.6400	$935.65	$935.65	$935.60