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	$52.93	9.533%	$57.9758	$57.98	$58.00	$58.00
Purchase #2	$107.48	9.541%	$117.7347	$117.73	$117.75	$117.70
Purchase #3	$33.49	11.276%	$37.2663	$37.27	$37.25	$37.30
Purchase #4	$121.40	5.236%	$127.7565	$127.76	$127.75	$127.80
Purchase #5	$177.40	10.664%	$196.3179	$196.32	$196.30	$196.30
Purchase #6	$240.52	5.236%	$253.1136	$253.11	$253.10	$253.10
Purchase #7	$226.68	13.532%	$257.3543	$257.35	$257.35	$257.40
7 purchase totals =	$959.90		$1,047.5191	$1,047.52	$1,047.50	$1,047.60