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	$208.33	6.827%	$222.5527	$222.55	$222.55	$222.60
Purchase #2	$94.65	4.746%	$99.1421	$99.14	$99.15	$99.10
Purchase #3	$152.63	7.478%	$164.0437	$164.04	$164.05	$164.00
Purchase #4	$82.46	5.337%	$86.8609	$86.86	$86.85	$86.90
Purchase #5	$191.93	12.349%	$215.6314	$215.63	$215.65	$215.60
Purchase #6	$214.89	9.465%	$235.2293	$235.23	$235.25	$235.20
Purchase #7	$74.95	10.412%	$82.7538	$82.75	$82.75	$82.80
7 purchase totals =	$1,019.84		$1,106.2139	$1,106.20	$1,106.25	$1,106.20