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	$115.87	4.111%	$120.6334	$120.63	$120.65	$120.60
Purchase #2	$90.35	5.699%	$95.499	$95.50	$95.50	$95.50
Purchase #3	$239.61	3.598%	$248.2312	$248.23	$248.25	$248.20
Purchase #4	$37.98	8.728%	$41.2949	$41.29	$41.30	$41.30
Purchase #5	$166.59	8.170%	$180.2004	$180.20	$180.20	$180.20
Purchase #6	$144.96	11.768%	$162.0189	$162.02	$162.00	$162.00
Purchase #7	$162.96	5.111%	$171.2889	$171.29	$171.30	$171.30
7 purchase totals =	$958.32		$1,019.1667	$1,019.16	$1,019.20	$1,019.10