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	$208.53	12.256%	$234.0874	$234.09	$234.10	$234.10
Purchase #2	$89.48	11.793%	$100.0324	$100.03	$100.05	$100.00
Purchase #3	$52.40	12.404%	$58.8997	$58.90	$58.90	$58.90
Purchase #4	$99.71	9.467%	$109.1495	$109.15	$109.15	$109.10
Purchase #5	$150.97	11.517%	$168.3572	$168.36	$168.35	$168.40
Purchase #6	$231.42	9.797%	$254.0922	$254.09	$254.10	$254.10
Purchase #7	$79.80	12.307%	$89.621	$89.62	$89.60	$89.60
7 purchase totals =	$912.31		$1,014.2394	$1,014.24	$1,014.25	$1,014.20