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	$37.51	3.805%	$38.9373	$38.94	$38.95	$38.90
Purchase #2	$100.81	8.824%	$109.7055	$109.71	$109.70	$109.70
Purchase #3	$210.82	4.610%	$220.5388	$220.54	$220.55	$220.50
Purchase #4	$159.36	5.671%	$168.3973	$168.40	$168.40	$168.40
Purchase #5	$164.87	7.198%	$176.7373	$176.74	$176.75	$176.70
Purchase #6	$229.81	11.142%	$255.4154	$255.42	$255.40	$255.40
Purchase #7	$172.68	3.482%	$178.6927	$178.69	$178.70	$178.70
7 purchase totals =	$1,075.86		$1,148.4243	$1,148.44	$1,148.45	$1,148.30