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	$170.88	4.613%	$178.7627	$178.76	$178.75	$178.80
Purchase #2	$98.31	13.744%	$111.8217	$111.82	$111.80	$111.80
Purchase #3	$75.83	6.538%	$80.7878	$80.79	$80.80	$80.80
Purchase #4	$125.95	12.348%	$141.5023	$141.50	$141.50	$141.50
Purchase #5	$138.62	10.617%	$153.3373	$153.34	$153.35	$153.30
Purchase #6	$181.59	11.142%	$201.8228	$201.82	$201.80	$201.80
Purchase #7	$180.49	10.810%	$200.001	$200.00	$200.00	$200.00
7 purchase totals =	$971.67		$1,068.0356	$1,068.03	$1,068.00	$1,068.00