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	$102.42	10.315%	$112.9846	$112.98	$113.00	$113.00
Purchase #2	$147.62	7.279%	$158.3653	$158.37	$158.35	$158.40
Purchase #3	$35.40	8.253%	$38.3216	$38.32	$38.30	$38.30
Purchase #4	$172.95	6.756%	$184.6345	$184.63	$184.65	$184.60
Purchase #5	$111.90	6.265%	$118.9105	$118.91	$118.90	$118.90
Purchase #6	$94.41	10.253%	$104.0899	$104.09	$104.10	$104.10
Purchase #7	$125.89	12.445%	$141.557	$141.56	$141.55	$141.60
7 purchase totals =	$790.59		$858.8634	$858.86	$858.85	$858.90