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	$110.67	7.587%	$119.0665	$119.07	$119.05	$119.10
Purchase #2	$200.98	13.393%	$227.8973	$227.90	$227.90	$227.90
Purchase #3	$143.25	8.281%	$155.1125	$155.11	$155.10	$155.10
Purchase #4	$250.33	9.690%	$274.587	$274.59	$274.60	$274.60
Purchase #5	$39.64	6.774%	$42.3252	$42.33	$42.35	$42.30
Purchase #6	$91.88	6.712%	$98.047	$98.05	$98.05	$98.00
Purchase #7	$43.78	3.346%	$45.2449	$45.24	$45.25	$45.20
7 purchase totals =	$880.53		$962.2804	$962.29	$962.30	$962.20