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	$218.25	10.570%	$241.319	$241.32	$241.30	$241.30
Purchase #2	$22.83	13.383%	$25.8853	$25.89	$25.90	$25.90
Purchase #3	$152.25	5.104%	$160.0208	$160.02	$160.00	$160.00
Purchase #4	$196.58	12.414%	$220.9834	$220.98	$221.00	$221.00
Purchase #5	$105.31	5.486%	$111.0873	$111.09	$111.10	$111.10
Purchase #6	$146.63	13.726%	$166.7564	$166.76	$166.75	$166.80
Purchase #7	$103.60	11.701%	$115.7222	$115.72	$115.70	$115.70
7 purchase totals =	$945.45		$1,041.7744	$1,041.78	$1,041.75	$1,041.80