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	$132.39	5.680%	$139.9098	$139.91	$139.90	$139.90
Purchase #2	$179.85	9.631%	$197.1714	$197.17	$197.15	$197.20
Purchase #3	$174.34	4.415%	$182.0371	$182.04	$182.05	$182.00
Purchase #4	$121.98	4.684%	$127.6935	$127.69	$127.70	$127.70
Purchase #5	$143.94	12.739%	$162.2765	$162.28	$162.30	$162.30
Purchase #6	$139.59	10.249%	$153.8966	$153.90	$153.90	$153.90
Purchase #7	$120.46	9.380%	$131.7591	$131.76	$131.75	$131.80
7 purchase totals =	$1,012.55		$1,094.7440	$1,094.75	$1,094.75	$1,094.80