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	$143.88	10.874%	$159.5255	$159.53	$159.55	$159.50
Purchase #2	$136.46	7.805%	$147.1107	$147.11	$147.10	$147.10
Purchase #3	$245.59	5.191%	$258.3386	$258.34	$258.35	$258.30
Purchase #4	$168.88	10.222%	$186.1429	$186.14	$186.15	$186.10
Purchase #5	$72.94	7.727%	$78.5761	$78.58	$78.60	$78.60
Purchase #6	$136.79	5.816%	$144.7457	$144.75	$144.75	$144.70
Purchase #7	$138.60	5.128%	$145.7074	$145.71	$145.70	$145.70
7 purchase totals =	$1,043.14		$1,120.1469	$1,120.16	$1,120.20	$1,120.00