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	$223.69	4.536%	$233.8366	$233.84	$233.85	$233.80
Purchase #2	$125.80	3.273%	$129.9174	$129.92	$129.90	$129.90
Purchase #3	$28.52	9.803%	$31.3158	$31.32	$31.30	$31.30
Purchase #4	$53.68	5.508%	$56.6367	$56.64	$56.65	$56.60
Purchase #5	$31.91	7.860%	$34.4181	$34.42	$34.40	$34.40
Purchase #6	$86.41	5.138%	$90.8497	$90.85	$90.85	$90.80
Purchase #7	$181.56	3.788%	$188.4375	$188.44	$188.45	$188.40
7 purchase totals =	$731.57		$765.4118	$765.43	$765.40	$765.20