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	$53.85	7.594%	$57.9394	$57.94	$57.95	$57.90
Purchase #2	$232.47	13.116%	$262.9608	$262.96	$262.95	$263.00
Purchase #3	$219.46	4.613%	$229.5837	$229.58	$229.60	$229.60
Purchase #4	$102.87	6.159%	$109.2058	$109.21	$109.20	$109.20
Purchase #5	$13.59	4.706%	$14.2295	$14.23	$14.25	$14.20
Purchase #6	$168.52	3.567%	$174.5311	$174.53	$174.55	$174.50
Purchase #7	$156.31	10.156%	$172.1848	$172.18	$172.20	$172.20
7 purchase totals =	$947.07		$1,020.6351	$1,020.63	$1,020.70	$1,020.60