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	$248.87	5.521%	$262.6101	$262.61	$262.60	$262.60
Purchase #2	$76.27	12.591%	$85.8732	$85.87	$85.85	$85.90
Purchase #3	$180.77	7.806%	$194.8809	$194.88	$194.90	$194.90
Purchase #4	$89.98	9.121%	$98.1871	$98.19	$98.20	$98.20
Purchase #5	$111.88	4.247%	$116.6315	$116.63	$116.65	$116.60
Purchase #6	$73.85	4.419%	$77.1134	$77.11	$77.10	$77.10
Purchase #7	$223.65	12.193%	$250.9196	$250.92	$250.90	$250.90
7 purchase totals =	$1,005.27		$1,086.2158	$1,086.21	$1,086.20	$1,086.20