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	$92.84	9.139%	$101.3246	$101.32	$101.30	$101.30
Purchase #2	$99.97	11.336%	$111.3026	$111.30	$111.30	$111.30
Purchase #3	$13.43	7.498%	$14.437	$14.44	$14.45	$14.40
Purchase #4	$105.34	11.562%	$117.5194	$117.52	$117.50	$117.50
Purchase #5	$38.61	4.553%	$40.3679	$40.37	$40.35	$40.40
Purchase #6	$176.53	10.791%	$195.5794	$195.58	$195.60	$195.60
Purchase #7	$19.75	10.370%	$21.7981	$21.80	$21.80	$21.80
7 purchase totals =	$546.47		$602.3290	$602.33	$602.30	$602.30