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	$192.79	6.681%	$205.6703	$205.67	$205.65	$205.70
Purchase #2	$72.38	13.585%	$82.2128	$82.21	$82.20	$82.20
Purchase #3	$117.77	4.626%	$123.218	$123.22	$123.20	$123.20
Purchase #4	$84.99	12.497%	$95.6112	$95.61	$95.60	$95.60
Purchase #5	$211.68	10.332%	$233.5508	$233.55	$233.55	$233.60
Purchase #6	$196.36	13.466%	$222.8018	$222.80	$222.80	$222.80
Purchase #7	$199.95	11.846%	$223.6361	$223.64	$223.65	$223.60
7 purchase totals =	$1,075.92		$1,186.7010	$1,186.70	$1,186.65	$1,186.70