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	$141.28	5.437%	$148.9614	$148.96	$148.95	$149.00
Purchase #2	$112.81	10.436%	$124.5829	$124.58	$124.60	$124.60
Purchase #3	$155.51	8.250%	$168.3396	$168.34	$168.35	$168.30
Purchase #4	$51.80	5.368%	$54.5806	$54.58	$54.60	$54.60
Purchase #5	$147.80	3.846%	$153.4844	$153.48	$153.50	$153.50
Purchase #6	$31.69	7.645%	$34.1127	$34.11	$34.10	$34.10
Purchase #7	$120.96	8.712%	$131.498	$131.50	$131.50	$131.50
7 purchase totals =	$761.85		$815.5596	$815.55	$815.60	$815.60