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	$98.71	6.774%	$105.3966	$105.40	$105.40	$105.40
Purchase #2	$84.57	5.170%	$88.9423	$88.94	$88.95	$88.90
Purchase #3	$59.74	9.507%	$65.4195	$65.42	$65.40	$65.40
Purchase #4	$156.89	12.660%	$176.7523	$176.75	$176.75	$176.80
Purchase #5	$126.69	4.379%	$132.2378	$132.24	$132.25	$132.20
Purchase #6	$74.79	11.528%	$83.4118	$83.41	$83.40	$83.40
Purchase #7	$64.50	10.289%	$71.1364	$71.14	$71.15	$71.10
7 purchase totals =	$665.89		$723.2967	$723.30	$723.30	$723.20