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	$99.30	8.723%	$107.9619	$107.96	$107.95	$108.00
Purchase #2	$82.38	11.780%	$92.0844	$92.08	$92.10	$92.10
Purchase #3	$195.99	13.618%	$222.6799	$222.68	$222.70	$222.70
Purchase #4	$191.62	4.314%	$199.8865	$199.89	$199.90	$199.90
Purchase #5	$79.71	11.857%	$89.1612	$89.16	$89.15	$89.20
Purchase #6	$64.99	11.195%	$72.2656	$72.27	$72.25	$72.30
Purchase #7	$214.27	11.481%	$238.8703	$238.87	$238.85	$238.90
7 purchase totals =	$928.26		$1,022.9098	$1,022.91	$1,022.90	$1,023.10