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	$151.80	8.438%	$164.6089	$164.61	$164.60	$164.60
Purchase #2	$131.69	4.501%	$137.6174	$137.62	$137.60	$137.60
Purchase #3	$79.63	3.478%	$82.3995	$82.40	$82.40	$82.40
Purchase #4	$63.56	13.231%	$71.9696	$71.97	$71.95	$72.00
Purchase #5	$120.73	6.365%	$128.4145	$128.41	$128.40	$128.40
Purchase #6	$77.97	3.420%	$80.6366	$80.64	$80.65	$80.60
Purchase #7	$82.50	8.264%	$89.3178	$89.32	$89.30	$89.30
7 purchase totals =	$707.88		$754.9643	$754.97	$754.90	$754.90