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	$241.38	7.445%	$259.3507	$259.35	$259.35	$259.40
Purchase #2	$183.54	7.286%	$196.9127	$196.91	$196.90	$196.90
Purchase #3	$181.48	8.186%	$196.336	$196.34	$196.35	$196.30
Purchase #4	$26.72	10.792%	$29.6036	$29.60	$29.60	$29.60
Purchase #5	$113.68	4.541%	$118.8422	$118.84	$118.85	$118.80
Purchase #6	$140.71	3.847%	$146.1231	$146.12	$146.10	$146.10
Purchase #7	$134.36	8.137%	$145.2929	$145.29	$145.30	$145.30
7 purchase totals =	$1,021.87		$1,092.4612	$1,092.45	$1,092.45	$1,092.40