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	$127.29	10.105%	$140.1527	$140.15	$140.15	$140.20
Purchase #2	$250.83	9.143%	$273.7634	$273.76	$273.75	$273.80
Purchase #3	$89.50	11.457%	$99.754	$99.75	$99.75	$99.80
Purchase #4	$238.91	7.452%	$256.7136	$256.71	$256.70	$256.70
Purchase #5	$102.32	3.315%	$105.7119	$105.71	$105.70	$105.70
Purchase #6	$189.58	9.558%	$207.7001	$207.70	$207.70	$207.70
Purchase #7	$6.99	8.793%	$7.6046	$7.60	$7.60	$7.60
7 purchase totals =	$1,005.42		$1,091.4003	$1,091.38	$1,091.35	$1,091.50