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	$189.27	3.709%	$196.29	$196.29	$196.30	$196.30
Purchase #2	$130.96	5.259%	$137.8472	$137.85	$137.85	$137.80
Purchase #3	$150.74	11.723%	$168.4113	$168.41	$168.40	$168.40
Purchase #4	$6.45	9.462%	$7.0603	$7.06	$7.05	$7.10
Purchase #5	$22.69	5.415%	$23.9187	$23.92	$23.90	$23.90
Purchase #6	$8.33	3.385%	$8.612	$8.61	$8.60	$8.60
Purchase #7	$73.88	8.490%	$80.1524	$80.15	$80.15	$80.20
7 purchase totals =	$582.32		$622.2919	$622.29	$622.25	$622.30