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	$29.77	8.667%	$32.3502	$32.35	$32.35	$32.40
Purchase #2	$171.64	4.558%	$179.4634	$179.46	$179.45	$179.50
Purchase #3	$17.31	4.553%	$18.0981	$18.10	$18.10	$18.10
Purchase #4	$106.35	9.741%	$116.7096	$116.71	$116.70	$116.70
Purchase #5	$85.95	3.856%	$89.2642	$89.26	$89.25	$89.30
Purchase #6	$151.40	7.399%	$162.6021	$162.60	$162.60	$162.60
Purchase #7	$86.80	3.265%	$89.634	$89.63	$89.65	$89.60
7 purchase totals =	$649.22		$688.1216	$688.11	$688.10	$688.20