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	$208.44	11.725%	$232.8796	$232.88	$232.90	$232.90
Purchase #2	$66.55	4.169%	$69.3245	$69.32	$69.30	$69.30
Purchase #3	$149.64	12.452%	$168.2732	$168.27	$168.25	$168.30
Purchase #4	$142.59	13.594%	$161.9737	$161.97	$161.95	$162.00
Purchase #5	$245.72	3.416%	$254.1138	$254.11	$254.10	$254.10
Purchase #6	$81.26	10.499%	$89.7915	$89.79	$89.80	$89.80
Purchase #7	$164.67	5.581%	$173.8602	$173.86	$173.85	$173.90
7 purchase totals =	$1,058.87		$1,150.2165	$1,150.20	$1,150.15	$1,150.30