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	$116.56	10.376%	$128.6543	$128.65	$128.65	$128.70
Purchase #2	$77.78	5.637%	$82.1645	$82.16	$82.15	$82.20
Purchase #3	$96.91	10.448%	$107.0352	$107.04	$107.05	$107.00
Purchase #4	$179.63	11.365%	$200.0449	$200.04	$200.05	$200.00
Purchase #5	$212.62	11.170%	$236.3697	$236.37	$236.35	$236.40
Purchase #6	$101.48	9.521%	$111.1419	$111.14	$111.15	$111.10
Purchase #7	$9.43	6.325%	$10.0264	$10.03	$10.05	$10.00
7 purchase totals =	$794.41		$875.4369	$875.43	$875.45	$875.40