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	$158.27	4.530%	$165.4396	$165.44	$165.45	$165.40
Purchase #2	$86.27	3.727%	$89.4853	$89.49	$89.50	$89.50
Purchase #3	$160.77	13.441%	$182.3791	$182.38	$182.40	$182.40
Purchase #4	$37.55	10.206%	$41.3824	$41.38	$41.40	$41.40
Purchase #5	$118.84	5.306%	$125.1457	$125.15	$125.15	$125.10
Purchase #6	$16.87	6.159%	$17.909	$17.91	$17.90	$17.90
Purchase #7	$164.75	8.521%	$178.7883	$178.79	$178.80	$178.80
7 purchase totals =	$743.32		$800.5294	$800.54	$800.60	$800.50