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	$93.54	6.517%	$99.636	$99.64	$99.65	$99.60
Purchase #2	$49.28	9.864%	$54.141	$54.14	$54.15	$54.10
Purchase #3	$148.72	5.602%	$157.0513	$157.05	$157.05	$157.10
Purchase #4	$82.39	9.209%	$89.9773	$89.98	$90.00	$90.00
Purchase #5	$166.71	11.578%	$186.0117	$186.01	$186.00	$186.00
Purchase #6	$190.30	3.458%	$196.8806	$196.88	$196.90	$196.90
Purchase #7	$116.31	12.698%	$131.079	$131.08	$131.10	$131.10
7 purchase totals =	$847.25		$914.7769	$914.78	$914.85	$914.80