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	$54.68	11.600%	$61.0229	$61.02	$61.00	$61.00
Purchase #2	$125.41	5.207%	$131.9401	$131.94	$131.95	$131.90
Purchase #3	$196.46	13.239%	$222.4693	$222.47	$222.45	$222.50
Purchase #4	$164.70	9.684%	$180.6495	$180.65	$180.65	$180.60
Purchase #5	$30.61	7.268%	$32.8347	$32.83	$32.85	$32.80
Purchase #6	$115.62	3.700%	$119.8979	$119.90	$119.90	$119.90
Purchase #7	$96.26	11.528%	$107.3569	$107.36	$107.35	$107.40
7 purchase totals =	$783.74		$856.1713	$856.17	$856.15	$856.10