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	$150.46	13.588%	$170.9045	$170.90	$170.90	$170.90
Purchase #2	$7.56	9.124%	$8.2498	$8.25	$8.25	$8.20
Purchase #3	$177.72	10.414%	$196.2278	$196.23	$196.25	$196.20
Purchase #4	$198.37	9.120%	$216.4613	$216.46	$216.45	$216.50
Purchase #5	$120.96	6.124%	$128.3676	$128.37	$128.35	$128.40
Purchase #6	$62.57	13.767%	$71.184	$71.18	$71.20	$71.20
Purchase #7	$242.35	11.113%	$269.2824	$269.28	$269.30	$269.30
7 purchase totals =	$959.99		$1,060.6774	$1,060.67	$1,060.70	$1,060.70