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	$126.79	5.180%	$133.3577	$133.36	$133.35	$133.40
Purchase #2	$177.52	11.712%	$198.3111	$198.31	$198.30	$198.30
Purchase #3	$229.76	10.345%	$253.5287	$253.53	$253.55	$253.50
Purchase #4	$140.64	4.225%	$146.582	$146.58	$146.60	$146.60
Purchase #5	$144.32	8.145%	$156.0749	$156.07	$156.05	$156.10
Purchase #6	$78.66	9.225%	$85.9164	$85.92	$85.90	$85.90
Purchase #7	$96.94	12.746%	$109.296	$109.30	$109.30	$109.30
7 purchase totals =	$994.63		$1,083.0668	$1,083.07	$1,083.05	$1,083.10