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	$245.90	5.743%	$260.022	$260.02	$260.00	$260.00
Purchase #2	$91.72	11.154%	$101.9504	$101.95	$101.95	$102.00
Purchase #3	$203.40	4.662%	$212.8825	$212.88	$212.90	$212.90
Purchase #4	$21.71	13.857%	$24.7184	$24.72	$24.70	$24.70
Purchase #5	$159.39	4.527%	$166.6056	$166.61	$166.60	$166.60
Purchase #6	$79.34	4.320%	$82.7675	$82.77	$82.75	$82.80
Purchase #7	$179.38	11.686%	$200.3423	$200.34	$200.35	$200.30
7 purchase totals =	$980.84		$1,049.2887	$1,049.29	$1,049.25	$1,049.30