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	$162.65	11.488%	$181.3352	$181.34	$181.35	$181.30
Purchase #2	$151.95	10.234%	$167.5006	$167.50	$167.50	$167.50
Purchase #3	$97.93	3.379%	$101.2391	$101.24	$101.25	$101.20
Purchase #4	$159.58	5.671%	$168.6298	$168.63	$168.65	$168.60
Purchase #5	$73.65	8.527%	$79.9301	$79.93	$79.95	$79.90
Purchase #6	$100.85	4.753%	$105.6434	$105.64	$105.65	$105.60
Purchase #7	$86.32	4.178%	$89.9264	$89.93	$89.95	$89.90
7 purchase totals =	$832.93		$894.2046	$894.21	$894.30	$894.00