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	$133.59	12.530%	$150.3288	$150.33	$150.35	$150.30
Purchase #2	$6.91	10.265%	$7.6193	$7.62	$7.60	$7.60
Purchase #3	$92.96	10.679%	$102.8872	$102.89	$102.90	$102.90
Purchase #4	$120.69	6.701%	$128.7774	$128.78	$128.80	$128.80
Purchase #5	$61.98	9.581%	$67.9183	$67.92	$67.90	$67.90
Purchase #6	$70.83	10.187%	$78.0455	$78.05	$78.05	$78.00
Purchase #7	$225.31	4.522%	$235.4985	$235.50	$235.50	$235.50
7 purchase totals =	$712.27		$771.0750	$771.09	$771.10	$771.00