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	$54.59	12.752%	$61.5513	$61.55	$61.55	$61.60
Purchase #2	$141.44	10.745%	$156.6377	$156.64	$156.65	$156.60
Purchase #3	$199.70	5.626%	$210.9351	$210.94	$210.95	$210.90
Purchase #4	$180.26	8.811%	$196.1427	$196.14	$196.15	$196.10
Purchase #5	$159.35	4.352%	$166.2849	$166.28	$166.30	$166.30
Purchase #6	$111.61	5.654%	$117.9204	$117.92	$117.90	$117.90
Purchase #7	$174.74	3.163%	$180.267	$180.27	$180.25	$180.30
7 purchase totals =	$1,021.69		$1,089.7391	$1,089.74	$1,089.75	$1,089.70