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	$198.59	9.817%	$218.0856	$218.09	$218.10	$218.10
Purchase #2	$19.88	3.625%	$20.6007	$20.60	$20.60	$20.60
Purchase #3	$47.76	4.222%	$49.7764	$49.78	$49.80	$49.80
Purchase #4	$217.35	9.860%	$238.7807	$238.78	$238.80	$238.80
Purchase #5	$146.55	9.443%	$160.3887	$160.39	$160.40	$160.40
Purchase #6	$12.39	11.580%	$13.8248	$13.82	$13.80	$13.80
Purchase #7	$40.69	13.712%	$46.2694	$46.27	$46.25	$46.30
7 purchase totals =	$683.21		$747.7263	$747.73	$747.75	$747.80