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	$188.43	4.247%	$196.4326	$196.43	$196.45	$196.40
Purchase #2	$210.86	4.728%	$220.8295	$220.83	$220.85	$220.80
Purchase #3	$124.37	5.408%	$131.0959	$131.10	$131.10	$131.10
Purchase #4	$178.27	9.276%	$194.8063	$194.81	$194.80	$194.80
Purchase #5	$169.71	9.613%	$186.0242	$186.02	$186.00	$186.00
Purchase #6	$166.30	12.707%	$187.4317	$187.43	$187.45	$187.40
Purchase #7	$139.84	13.213%	$158.3171	$158.32	$158.30	$158.30
7 purchase totals =	$1,177.78		$1,274.9373	$1,274.94	$1,274.95	$1,274.80