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	$214.56	13.281%	$243.0557	$243.06	$243.05	$243.10
Purchase #2	$155.96	4.118%	$162.3824	$162.38	$162.40	$162.40
Purchase #3	$71.92	9.659%	$78.8668	$78.87	$78.85	$78.90
Purchase #4	$80.84	13.715%	$91.9272	$91.93	$91.95	$91.90
Purchase #5	$199.64	3.185%	$205.9985	$206.00	$206.00	$206.00
Purchase #6	$216.42	7.153%	$231.9005	$231.90	$231.90	$231.90
Purchase #7	$148.90	13.325%	$168.7409	$168.74	$168.75	$168.70
7 purchase totals =	$1,088.24		$1,182.8720	$1,182.88	$1,182.90	$1,182.90