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	$215.56	3.152%	$222.3545	$222.35	$222.35	$222.40
Purchase #2	$233.52	11.139%	$259.5318	$259.53	$259.55	$259.50
Purchase #3	$202.74	11.274%	$225.5969	$225.60	$225.60	$225.60
Purchase #4	$51.78	4.211%	$53.9605	$53.96	$53.95	$54.00
Purchase #5	$154.54	8.276%	$167.3297	$167.33	$167.35	$167.30
Purchase #6	$78.44	3.516%	$81.198	$81.20	$81.20	$81.20
Purchase #7	$182.32	10.200%	$200.9166	$200.92	$200.90	$200.90
7 purchase totals =	$1,118.90		$1,210.8880	$1,210.89	$1,210.90	$1,210.90