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	$218.47	8.605%	$237.2693	$237.27	$237.25	$237.30
Purchase #2	$230.41	11.781%	$257.5546	$257.55	$257.55	$257.60
Purchase #3	$81.86	9.410%	$89.563	$89.56	$89.55	$89.60
Purchase #4	$180.37	6.835%	$192.6983	$192.70	$192.70	$192.70
Purchase #5	$213.47	4.522%	$223.1231	$223.12	$223.10	$223.10
Purchase #6	$9.32	10.288%	$10.2788	$10.28	$10.30	$10.30
Purchase #7	$164.83	4.517%	$172.2754	$172.28	$172.30	$172.30
7 purchase totals =	$1,098.73		$1,182.7625	$1,182.76	$1,182.75	$1,182.90