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	$95.58	11.518%	$106.5889	$106.59	$106.60	$106.60
Purchase #2	$199.37	3.755%	$206.8563	$206.86	$206.85	$206.90
Purchase #3	$144.70	6.506%	$154.1142	$154.11	$154.10	$154.10
Purchase #4	$149.76	4.314%	$156.2206	$156.22	$156.20	$156.20
Purchase #5	$250.25	10.358%	$276.1709	$276.17	$276.15	$276.20
Purchase #6	$176.46	11.311%	$196.4194	$196.42	$196.40	$196.40
Purchase #7	$90.38	13.839%	$102.8877	$102.89	$102.90	$102.90
7 purchase totals =	$1,106.50		$1,199.2580	$1,199.26	$1,199.20	$1,199.30