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	$59.25	3.220%	$61.1579	$61.16	$61.15	$61.20
Purchase #2	$221.72	9.183%	$242.0805	$242.08	$242.10	$242.10
Purchase #3	$91.61	8.446%	$99.3474	$99.35	$99.35	$99.30
Purchase #4	$119.89	7.113%	$128.4178	$128.42	$128.40	$128.40
Purchase #5	$197.68	12.283%	$221.961	$221.96	$221.95	$222.00
Purchase #6	$132.88	3.260%	$137.2119	$137.21	$137.20	$137.20
Purchase #7	$190.93	10.296%	$210.5882	$210.59	$210.60	$210.60
7 purchase totals =	$1,013.96		$1,100.7647	$1,100.77	$1,100.75	$1,100.80