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	$153.65	5.775%	$162.5233	$162.52	$162.50	$162.50
Purchase #2	$175.56	10.424%	$193.8604	$193.86	$193.85	$193.90
Purchase #3	$102.34	11.522%	$114.1316	$114.13	$114.15	$114.10
Purchase #4	$163.89	13.225%	$185.5645	$185.56	$185.55	$185.60
Purchase #5	$213.62	6.248%	$226.967	$226.97	$226.95	$227.00
Purchase #6	$18.25	9.869%	$20.0511	$20.05	$20.05	$20.10
Purchase #7	$147.91	3.365%	$152.8872	$152.89	$152.90	$152.90
7 purchase totals =	$975.22		$1,055.9851	$1,055.98	$1,055.95	$1,056.10