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	$146.82	3.202%	$151.5212	$151.52	$151.50	$151.50
Purchase #2	$81.98	8.581%	$89.0147	$89.01	$89.00	$89.00
Purchase #3	$95.90	7.604%	$103.1922	$103.19	$103.20	$103.20
Purchase #4	$56.36	5.119%	$59.2451	$59.25	$59.25	$59.20
Purchase #5	$166.30	8.474%	$180.3923	$180.39	$180.40	$180.40
Purchase #6	$192.74	7.376%	$206.9565	$206.96	$206.95	$207.00
Purchase #7	$141.35	3.823%	$146.7538	$146.75	$146.75	$146.80
7 purchase totals =	$881.45		$937.0758	$937.07	$937.05	$937.10