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	$185.27	6.305%	$196.9513	$196.95	$196.95	$197.00
Purchase #2	$103.67	11.433%	$115.5226	$115.52	$115.50	$115.50
Purchase #3	$8.55	11.747%	$9.5544	$9.55	$9.55	$9.60
Purchase #4	$133.88	9.273%	$146.2947	$146.29	$146.30	$146.30
Purchase #5	$118.76	10.702%	$131.4697	$131.47	$131.45	$131.50
Purchase #6	$184.61	11.524%	$205.8845	$205.88	$205.90	$205.90
Purchase #7	$127.31	9.783%	$139.7647	$139.76	$139.75	$139.80
7 purchase totals =	$862.05		$945.4419	$945.42	$945.40	$945.60