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	$145.67	3.346%	$150.5441	$150.54	$150.55	$150.50
Purchase #2	$175.99	8.787%	$191.4542	$191.45	$191.45	$191.50
Purchase #3	$117.83	6.296%	$125.2486	$125.25	$125.25	$125.20
Purchase #4	$79.49	11.276%	$88.4533	$88.45	$88.45	$88.50
Purchase #5	$203.81	4.754%	$213.4991	$213.50	$213.50	$213.50
Purchase #6	$234.36	12.870%	$264.5221	$264.52	$264.50	$264.50
Purchase #7	$98.82	6.834%	$105.5734	$105.57	$105.55	$105.60
7 purchase totals =	$1,055.97		$1,139.2948	$1,139.28	$1,139.25	$1,139.30