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	$152.92	8.850%	$166.4534	$166.45	$166.45	$166.50
Purchase #2	$72.46	7.612%	$77.9757	$77.98	$78.00	$78.00
Purchase #3	$36.82	7.512%	$39.5859	$39.59	$39.60	$39.60
Purchase #4	$153.88	6.533%	$163.933	$163.93	$163.95	$163.90
Purchase #5	$100.26	9.243%	$109.527	$109.53	$109.55	$109.50
Purchase #6	$29.53	6.531%	$31.4586	$31.46	$31.45	$31.50
Purchase #7	$237.45	7.143%	$254.4111	$254.41	$254.40	$254.40
7 purchase totals =	$783.32		$843.3447	$843.35	$843.40	$843.40