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	$9.53	11.223%	$10.5996	$10.60	$10.60	$10.60
Purchase #2	$179.64	9.274%	$196.2998	$196.30	$196.30	$196.30
Purchase #3	$148.54	3.519%	$153.7671	$153.77	$153.75	$153.80
Purchase #4	$110.55	13.727%	$125.7252	$125.73	$125.75	$125.70
Purchase #5	$127.43	12.541%	$143.411	$143.41	$143.40	$143.40
Purchase #6	$41.85	12.329%	$47.0097	$47.01	$47.00	$47.00
Purchase #7	$123.27	6.757%	$131.5994	$131.60	$131.60	$131.60
7 purchase totals =	$740.81		$808.4118	$808.42	$808.40	$808.40