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	$27.29	7.695%	$29.39	$29.39	$29.40	$29.40
Purchase #2	$89.78	11.265%	$99.8937	$99.89	$99.90	$99.90
Purchase #3	$103.70	11.423%	$115.5457	$115.55	$115.55	$115.50
Purchase #4	$228.85	4.269%	$238.6196	$238.62	$238.60	$238.60
Purchase #5	$201.72	4.399%	$210.5937	$210.59	$210.60	$210.60
Purchase #6	$214.34	6.589%	$228.4629	$228.46	$228.45	$228.50
Purchase #7	$86.44	7.602%	$93.0112	$93.01	$93.00	$93.00
7 purchase totals =	$952.12		$1,015.5168	$1,015.51	$1,015.50	$1,015.50