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	$7.72	5.187%	$8.1204	$8.12	$8.10	$8.10
Purchase #2	$17.84	8.315%	$19.3234	$19.32	$19.30	$19.30
Purchase #3	$49.44	6.585%	$52.6956	$52.70	$52.70	$52.70
Purchase #4	$52.87	3.654%	$54.8019	$54.80	$54.80	$54.80
Purchase #5	$67.27	7.408%	$72.2534	$72.25	$72.25	$72.30
Purchase #6	$41.54	6.770%	$44.3523	$44.35	$44.35	$44.40
Purchase #7	$26.78	6.431%	$28.5022	$28.50	$28.50	$28.50
7 purchase totals =	$263.46		$280.0492	$280.04	$280.00	$280.10