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	$136.94	4.355%	$142.9037	$142.90	$142.90	$142.90
Purchase #2	$117.76	8.299%	$127.5329	$127.53	$127.55	$127.50
Purchase #3	$125.70	6.716%	$134.142	$134.14	$134.15	$134.10
Purchase #4	$229.92	12.389%	$258.4048	$258.40	$258.40	$258.40
Purchase #5	$108.72	9.644%	$119.205	$119.21	$119.20	$119.20
Purchase #6	$112.42	3.683%	$116.5604	$116.56	$116.55	$116.60
Purchase #7	$242.33	13.873%	$275.9484	$275.95	$275.95	$275.90
7 purchase totals =	$1,073.79		$1,174.6972	$1,174.69	$1,174.70	$1,174.60