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	$104.34	6.729%	$111.361	$111.36	$111.35	$111.40
Purchase #2	$150.97	11.396%	$168.1745	$168.17	$168.15	$168.20
Purchase #3	$213.39	10.752%	$236.3337	$236.33	$236.35	$236.30
Purchase #4	$39.30	7.457%	$42.2306	$42.23	$42.25	$42.20
Purchase #5	$248.82	9.324%	$272.02	$272.02	$272.00	$272.00
Purchase #6	$60.64	5.712%	$64.1038	$64.10	$64.10	$64.10
Purchase #7	$58.69	4.107%	$61.1004	$61.10	$61.10	$61.10
7 purchase totals =	$876.15		$955.3240	$955.31	$955.30	$955.30