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	$94.67	9.673%	$103.8274	$103.83	$103.85	$103.80
Purchase #2	$79.25	7.327%	$85.0566	$85.06	$85.05	$85.10
Purchase #3	$221.85	5.327%	$233.6679	$233.67	$233.65	$233.70
Purchase #4	$177.29	10.727%	$196.3079	$196.31	$196.30	$196.30
Purchase #5	$140.56	13.215%	$159.135	$159.14	$159.15	$159.10
Purchase #6	$191.99	13.256%	$217.4402	$217.44	$217.45	$217.40
Purchase #7	$85.54	11.153%	$95.0803	$95.08	$95.10	$95.10
7 purchase totals =	$991.15		$1,090.5153	$1,090.53	$1,090.55	$1,090.50