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	$139.88	5.679%	$147.8238	$147.82	$147.80	$147.80
Purchase #2	$59.37	13.273%	$67.2502	$67.25	$67.25	$67.30
Purchase #3	$241.33	5.803%	$255.3344	$255.33	$255.35	$255.30
Purchase #4	$36.38	9.363%	$39.7863	$39.79	$39.80	$39.80
Purchase #5	$168.93	4.220%	$176.0588	$176.06	$176.05	$176.10
Purchase #6	$85.50	11.844%	$95.6266	$95.63	$95.65	$95.60
Purchase #7	$199.36	10.642%	$220.5759	$220.58	$220.60	$220.60
7 purchase totals =	$930.75		$1,002.4560	$1,002.46	$1,002.50	$1,002.50