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	$215.52	3.501%	$223.0654	$223.07	$223.05	$223.10
Purchase #2	$23.68	13.526%	$26.883	$26.88	$26.90	$26.90
Purchase #3	$184.92	11.355%	$205.9177	$205.92	$205.90	$205.90
Purchase #4	$218.71	9.211%	$238.8554	$238.86	$238.85	$238.90
Purchase #5	$96.67	10.321%	$106.6473	$106.65	$106.65	$106.60
Purchase #6	$238.86	4.379%	$249.3197	$249.32	$249.30	$249.30
Purchase #7	$91.76	9.366%	$100.3542	$100.35	$100.35	$100.40
7 purchase totals =	$1,070.12		$1,151.0427	$1,151.05	$1,151.00	$1,151.10