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	$205.96	10.461%	$227.5055	$227.51	$227.50	$227.50
Purchase #2	$82.63	3.508%	$85.5287	$85.53	$85.55	$85.50
Purchase #3	$159.64	13.114%	$180.5752	$180.58	$180.60	$180.60
Purchase #4	$249.56	10.321%	$275.3171	$275.32	$275.30	$275.30
Purchase #5	$150.88	5.606%	$159.3383	$159.34	$159.35	$159.30
Purchase #6	$186.56	13.699%	$212.1169	$212.12	$212.10	$212.10
Purchase #7	$36.83	11.193%	$40.9524	$40.95	$40.95	$41.00
7 purchase totals =	$1,072.06		$1,181.3341	$1,181.35	$1,181.35	$1,181.30