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	$105.74	5.241%	$111.2818	$111.28	$111.30	$111.30
Purchase #2	$91.88	8.216%	$99.4289	$99.43	$99.45	$99.40
Purchase #3	$81.81	11.184%	$90.9596	$90.96	$90.95	$91.00
Purchase #4	$213.97	11.173%	$237.8769	$237.88	$237.90	$237.90
Purchase #5	$31.35	3.224%	$32.3607	$32.36	$32.35	$32.40
Purchase #6	$77.78	3.284%	$80.3343	$80.33	$80.35	$80.30
Purchase #7	$39.71	7.523%	$42.6974	$42.70	$42.70	$42.70
7 purchase totals =	$642.24		$694.9396	$694.94	$695.00	$695.00