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	$91.59	5.526%	$96.6513	$96.65	$96.65	$96.70
Purchase #2	$150.62	3.618%	$156.0694	$156.07	$156.05	$156.10
Purchase #3	$123.36	12.777%	$139.1217	$139.12	$139.10	$139.10
Purchase #4	$29.59	7.537%	$31.8202	$31.82	$31.80	$31.80
Purchase #5	$119.75	4.311%	$124.9124	$124.91	$124.90	$124.90
Purchase #6	$6.58	7.845%	$7.0962	$7.10	$7.10	$7.10
Purchase #7	$65.46	10.502%	$72.3346	$72.33	$72.35	$72.30
7 purchase totals =	$586.95		$628.0058	$628.00	$627.95	$628.00