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	$99.31	7.127%	$106.3878	$106.39	$106.40	$106.40
Purchase #2	$127.54	11.205%	$141.8309	$141.83	$141.85	$141.80
Purchase #3	$148.31	10.675%	$164.1421	$164.14	$164.15	$164.10
Purchase #4	$207.85	3.582%	$215.2952	$215.30	$215.30	$215.30
Purchase #5	$227.56	11.727%	$254.246	$254.25	$254.25	$254.20
Purchase #6	$9.76	13.372%	$11.0651	$11.07	$11.05	$11.10
Purchase #7	$49.80	3.510%	$51.548	$51.55	$51.55	$51.50
7 purchase totals =	$870.13		$944.5151	$944.53	$944.55	$944.40