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	$151.60	11.700%	$169.3372	$169.34	$169.35	$169.30
Purchase #2	$139.46	9.164%	$152.2401	$152.24	$152.25	$152.20
Purchase #3	$20.55	4.413%	$21.4569	$21.46	$21.45	$21.50
Purchase #4	$218.41	12.818%	$246.4058	$246.41	$246.40	$246.40
Purchase #5	$140.46	3.325%	$145.1303	$145.13	$145.15	$145.10
Purchase #6	$86.60	4.213%	$90.2485	$90.25	$90.25	$90.20
Purchase #7	$167.80	3.118%	$173.032	$173.03	$173.05	$173.00
7 purchase totals =	$924.88		$997.8508	$997.86	$997.90	$997.70