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	$207.79	5.792%	$219.8252	$219.83	$219.85	$219.80
Purchase #2	$44.72	13.847%	$50.9124	$50.91	$50.90	$50.90
Purchase #3	$173.85	11.646%	$194.0966	$194.10	$194.10	$194.10
Purchase #4	$228.56	6.715%	$243.9078	$243.91	$243.90	$243.90
Purchase #5	$115.54	10.405%	$127.5619	$127.56	$127.55	$127.60
Purchase #6	$244.59	11.763%	$273.3611	$273.36	$273.35	$273.40
Purchase #7	$131.59	8.299%	$142.5107	$142.51	$142.50	$142.50
7 purchase totals =	$1,146.64		$1,252.1757	$1,252.18	$1,252.15	$1,252.20