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	$14.48	11.386%	$16.1287	$16.13	$16.15	$16.10
Purchase #2	$97.85	3.822%	$101.5898	$101.59	$101.60	$101.60
Purchase #3	$54.80	13.801%	$62.3629	$62.36	$62.35	$62.40
Purchase #4	$71.93	6.227%	$76.4091	$76.41	$76.40	$76.40
Purchase #5	$226.61	12.211%	$254.2813	$254.28	$254.30	$254.30
Purchase #6	$182.52	9.655%	$200.1423	$200.14	$200.15	$200.10
Purchase #7	$69.41	4.518%	$72.5459	$72.55	$72.55	$72.50
7 purchase totals =	$717.60		$783.4600	$783.46	$783.50	$783.40