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	$56.77	8.142%	$61.3922	$61.39	$61.40	$61.40
Purchase #2	$134.60	13.867%	$153.265	$153.27	$153.25	$153.30
Purchase #3	$131.31	8.429%	$142.3781	$142.38	$142.40	$142.40
Purchase #4	$220.27	11.231%	$245.0085	$245.01	$245.00	$245.00
Purchase #5	$116.25	12.461%	$130.7359	$130.74	$130.75	$130.70
Purchase #6	$67.76	6.794%	$72.3636	$72.36	$72.35	$72.40
Purchase #7	$182.33	11.509%	$203.3144	$203.31	$203.30	$203.30
7 purchase totals =	$909.29		$1,008.4577	$1,008.46	$1,008.45	$1,008.50