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	$222.42	13.867%	$253.263	$253.26	$253.25	$253.30
Purchase #2	$168.31	3.109%	$173.5428	$173.54	$173.55	$173.50
Purchase #3	$88.56	11.330%	$98.5938	$98.59	$98.60	$98.60
Purchase #4	$203.57	12.852%	$229.7328	$229.73	$229.75	$229.70
Purchase #5	$167.39	5.152%	$176.0139	$176.01	$176.00	$176.00
Purchase #6	$85.61	12.761%	$96.5347	$96.53	$96.55	$96.50
Purchase #7	$104.95	13.517%	$119.1361	$119.14	$119.15	$119.10
7 purchase totals =	$1,040.81		$1,146.8171	$1,146.80	$1,146.85	$1,146.70