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	$97.49	13.597%	$110.7457	$110.75	$110.75	$110.70
Purchase #2	$123.92	5.858%	$131.1792	$131.18	$131.20	$131.20
Purchase #3	$81.70	11.275%	$90.9117	$90.91	$90.90	$90.90
Purchase #4	$92.41	12.412%	$103.8799	$103.88	$103.90	$103.90
Purchase #5	$232.85	8.762%	$253.2523	$253.25	$253.25	$253.30
Purchase #6	$191.44	13.768%	$217.7975	$217.80	$217.80	$217.80
Purchase #7	$136.46	10.215%	$150.3994	$150.40	$150.40	$150.40
7 purchase totals =	$956.27		$1,058.1657	$1,058.17	$1,058.20	$1,058.20