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	$89.52	3.294%	$92.4688	$92.47	$92.45	$92.50
Purchase #2	$178.94	9.612%	$196.1397	$196.14	$196.15	$196.10
Purchase #3	$39.70	11.645%	$44.3231	$44.32	$44.30	$44.30
Purchase #4	$185.58	7.387%	$199.2888	$199.29	$199.30	$199.30
Purchase #5	$233.94	4.110%	$243.5549	$243.55	$243.55	$243.60
Purchase #6	$105.98	11.258%	$117.9112	$117.91	$117.90	$117.90
Purchase #7	$22.59	7.527%	$24.2903	$24.29	$24.30	$24.30
7 purchase totals =	$856.25		$917.9768	$917.97	$917.95	$918.00