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	$121.71	3.311%	$125.7398	$125.74	$125.75	$125.70
Purchase #2	$37.31	9.792%	$40.9634	$40.96	$40.95	$41.00
Purchase #3	$217.27	8.479%	$235.6923	$235.69	$235.70	$235.70
Purchase #4	$241.75	5.424%	$254.8625	$254.86	$254.85	$254.90
Purchase #5	$96.65	13.393%	$109.5943	$109.59	$109.60	$109.60
Purchase #6	$90.40	5.437%	$95.315	$95.32	$95.30	$95.30
Purchase #7	$129.28	8.280%	$139.9844	$139.98	$140.00	$140.00
7 purchase totals =	$934.37		$1,002.1517	$1,002.14	$1,002.15	$1,002.20