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	$93.78	4.869%	$98.3461	$98.35	$98.35	$98.30
Purchase #2	$30.75	3.384%	$31.7906	$31.79	$31.80	$31.80
Purchase #3	$145.79	13.862%	$165.9994	$166.00	$166.00	$166.00
Purchase #4	$78.77	12.144%	$88.3358	$88.34	$88.35	$88.30
Purchase #5	$148.27	7.140%	$158.8565	$158.86	$158.85	$158.90
Purchase #6	$98.82	6.728%	$105.4686	$105.47	$105.45	$105.50
Purchase #7	$64.94	3.109%	$66.959	$66.96	$66.95	$67.00
7 purchase totals =	$661.12		$715.7560	$715.77	$715.75	$715.80