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	$128.82	10.265%	$142.0434	$142.04	$142.05	$142.00
Purchase #2	$204.62	11.505%	$228.1615	$228.16	$228.15	$228.20
Purchase #3	$53.30	11.259%	$59.301	$59.30	$59.30	$59.30
Purchase #4	$211.99	9.652%	$232.4513	$232.45	$232.45	$232.50
Purchase #5	$129.79	9.421%	$142.0175	$142.02	$142.00	$142.00
Purchase #6	$30.75	13.442%	$34.8834	$34.88	$34.90	$34.90
Purchase #7	$158.78	6.182%	$168.5958	$168.60	$168.60	$168.60
7 purchase totals =	$918.05		$1,007.4539	$1,007.45	$1,007.45	$1,007.50