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	$159.54	12.708%	$179.8143	$179.81	$179.80	$179.80
Purchase #2	$159.74	7.795%	$172.1917	$172.19	$172.20	$172.20
Purchase #3	$210.27	5.208%	$221.2209	$221.22	$221.20	$221.20
Purchase #4	$20.33	6.320%	$21.6149	$21.61	$21.60	$21.60
Purchase #5	$21.84	12.801%	$24.6357	$24.64	$24.65	$24.60
Purchase #6	$202.56	4.301%	$211.2721	$211.27	$211.25	$211.30
Purchase #7	$196.35	11.137%	$218.2175	$218.22	$218.20	$218.20
7 purchase totals =	$970.63		$1,048.9671	$1,048.96	$1,048.90	$1,048.90