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	$168.76	9.807%	$185.3103	$185.31	$185.30	$185.30
Purchase #2	$203.64	5.103%	$214.0317	$214.03	$214.05	$214.00
Purchase #3	$57.83	6.423%	$61.5444	$61.54	$61.55	$61.50
Purchase #4	$48.61	7.517%	$52.264	$52.26	$52.25	$52.30
Purchase #5	$92.87	11.813%	$103.8407	$103.84	$103.85	$103.80
Purchase #6	$109.35	6.493%	$116.4501	$116.45	$116.45	$116.50
Purchase #7	$25.89	11.560%	$28.8829	$28.88	$28.90	$28.90
7 purchase totals =	$706.95		$762.3241	$762.31	$762.35	$762.30